<?php

/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2019 - 2022, CodeIgniter Foundation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package CodeIgniter
 * @author  EllisLab Dev Team
 * @copyright   Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
 * @copyright   Copyright (c) 2014 - 2019, British Columbia Institute of Technology (https://bcit.ca/)
 * @copyright   Copyright (c) 2019 - 2022, CodeIgniter Foundation (https://codeigniter.com/)
 * @license https://opensource.org/licenses/MIT MIT License
 * @link    https://codeigniter.com
 * @since   Version 1.0.0
 * @filesource
 */

defined('BASEPATH') or exit('No direct script access allowed');

/**
 * CodeIgniter Email Class
 *
 * Permits email to be sent using Mail, Sendmail, or SMTP.
 *
 * @package     CodeIgniter
 * @subpackage  Libraries
 * @category    Libraries
 * @author      EllisLab Dev Team
 * @link        https://codeigniter.com/userguide3/libraries/email.html
 */
class CI_Email
{
    /**
     * Used as the User-Agent and X-Mailer headers' value.
     *
     * @var string
     */
    public $useragent   = 'CodeIgniter';

    /**
     * Path to the Sendmail binary.
     *
     * @var string
     */
    public $mailpath    = '/usr/sbin/sendmail'; // Sendmail path

    /**
     * Which method to use for sending e-mails.
     *
     * @var string  'mail', 'sendmail' or 'smtp'
     */
    public $protocol    = 'mail';       // mail/sendmail/smtp

    /**
     * STMP Server host
     *
     * @var string
     */
    public $smtp_host   = '';

    /**
     * SMTP Username
     *
     * @var string
     */
    public $smtp_user   = '';

    /**
     * SMTP Password
     *
     * @var string
     */
    public $smtp_pass   = '';

    /**
     * SMTP Server port
     *
     * @var int
     */
    public $smtp_port   = 25;

    /**
     * SMTP connection timeout in seconds
     *
     * @var int
     */
    public $smtp_timeout    = 5;

    /**
     * SMTP persistent connection
     *
     * @var bool
     */
    public $smtp_keepalive  = false;

    /**
     * SMTP Encryption
     *
     * @var string  empty, 'tls' or 'ssl'
     */
    public $smtp_crypto = '';

    /**
     * Whether to apply word-wrapping to the message body.
     *
     * @var bool
     */
    public $wordwrap    = true;

    /**
     * Number of characters to wrap at.
     *
     * @see CI_Email::$wordwrap
     * @var int
     */
    public $wrapchars   = 76;

    /**
     * Message format.
     *
     * @var string  'text' or 'html'
     */
    public $mailtype    = 'text';

    /**
     * Character set (default: utf-8)
     *
     * @var string
     */
    public $charset     = 'UTF-8';

    /**
     * Alternative message (for HTML messages only)
     *
     * @var string
     */
    public $alt_message = '';

    /**
     * Whether to validate e-mail addresses.
     *
     * @var bool
     */
    public $validate    = false;

    /**
     * X-Priority header value.
     *
     * @var int 1-5
     */
    public $priority    = 3;            // Default priority (1 - 5)

    /**
     * Newline character sequence.
     * Use "\r\n" to comply with RFC 822.
     *
     * @link    http://www.ietf.org/rfc/rfc822.txt
     * @var string  "\r\n" or "\n"
     */
    public $newline     = "\n";         // Default newline. "\r\n" or "\n" (Use "\r\n" to comply with RFC 822)

    /**
     * CRLF character sequence
     *
     * RFC 2045 specifies that for 'quoted-printable' encoding,
     * "\r\n" must be used. However, it appears that some servers
     * (even on the receiving end) don't handle it properly and
     * switching to "\n", while improper, is the only solution
     * that seems to work for all environments.
     *
     * @link    http://www.ietf.org/rfc/rfc822.txt
     * @var string
     */
    public $crlf        = "\n";

    /**
     * Whether to use Delivery Status Notification.
     *
     * @var bool
     */
    public $dsn     = false;

    /**
     * Whether to send multipart alternatives.
     * Yahoo! doesn't seem to like these.
     *
     * @var bool
     */
    public $send_multipart  = true;

    /**
     * Whether to send messages to BCC recipients in batches.
     *
     * @var bool
     */
    public $bcc_batch_mode  = false;

    /**
     * BCC Batch max number size.
     *
     * @see CI_Email::$bcc_batch_mode
     * @var int
     */
    public $bcc_batch_size  = 200;

    // --------------------------------------------------------------------

    /**
     * Whether PHP is running in safe mode. Initialized by the class constructor.
     *
     * @var bool
     */
    protected $_safe_mode       = false;

    /**
     * Subject header
     *
     * @var string
     */
    protected $_subject     = '';

    /**
     * Message body
     *
     * @var string
     */
    protected $_body        = '';

    /**
     * Final message body to be sent.
     *
     * @var string
     */
    protected $_finalbody       = '';

    /**
     * Final headers to send
     *
     * @var string
     */
    protected $_header_str      = '';

    /**
     * SMTP Connection socket placeholder
     *
     * @var resource
     */
    protected $_smtp_connect    = '';

    /**
     * Mail encoding
     *
     * @var string  '8bit' or '7bit'
     */
    protected $_encoding        = '8bit';

    /**
     * Whether to perform SMTP authentication
     *
     * @var bool
     */
    protected $_smtp_auth       = false;

    /**
     * Whether to send a Reply-To header
     *
     * @var bool
     */
    protected $_replyto_flag    = false;

    /**
     * Debug messages
     *
     * @see CI_Email::print_debugger()
     * @var string
     */
    protected $_debug_msg       = array();

    /**
     * Recipients
     *
     * @var string[]
     */
    protected $_recipients      = array();

    /**
     * CC Recipients
     *
     * @var string[]
     */
    protected $_cc_array        = array();

    /**
     * BCC Recipients
     *
     * @var string[]
     */
    protected $_bcc_array       = array();

    /**
     * Message headers
     *
     * @var string[]
     */
    protected $_headers     = array();

    /**
     * Attachment data
     *
     * @var array
     */
    protected $_attachments     = array();

    /**
     * Valid $protocol values
     *
     * @see CI_Email::$protocol
     * @var string[]
     */
    protected $_protocols       = array('mail', 'sendmail', 'smtp');

    /**
     * Base charsets
     *
     * Character sets valid for 7-bit encoding,
     * excluding language suffix.
     *
     * @var string[]
     */
    protected $_base_charsets   = array('us-ascii', 'iso-2022-');

    /**
     * Bit depths
     *
     * Valid mail encodings
     *
     * @see CI_Email::$_encoding
     * @var string[]
     */
    protected $_bit_depths      = array('7bit', '8bit');

    /**
     * $priority translations
     *
     * Actual values to send with the X-Priority header
     *
     * @var string[]
     */
    protected $_priorities = array(
        1 => '1 (Highest)',
        2 => '2 (High)',
        3 => '3 (Normal)',
        4 => '4 (Low)',
        5 => '5 (Lowest)'
    );

    /**
     * mbstring.func_overload flag
     *
     * @var bool
     */
    protected static $func_overload;

    // --------------------------------------------------------------------

    /**
     * Constructor - Sets Email Preferences
     *
     * The constructor can be passed an array of config values
     *
     * @param   array   $config = array()
     * @return  void
     */
    public function __construct(array $config = array())
    {
        $this->charset = config_item('charset');
        $this->initialize($config);
        $this->_safe_mode = (! is_php('5.4') && ini_get('safe_mode'));

        isset(self::$func_overload) or self::$func_overload = (! is_php('8.0') && extension_loaded('mbstring') && @ini_get('mbstring.func_overload'));

        log_message('info', 'Email Class Initialized');
    }

    // --------------------------------------------------------------------

    /**
     * Initialize preferences
     *
     * @param   array   $config
     * @return  CI_Email
     */
    public function initialize(array $config = array())
    {
        $this->clear();

        foreach ($config as $key => $val) {
            if (isset($this->$key)) {
                $method = 'set_' . $key;

                if (method_exists($this, $method)) {
                    $this->$method($val);
                } else {
                    $this->$key = $val;
                }
            }
        }

        $this->charset = strtoupper($this->charset);
        $this->_smtp_auth = isset($this->smtp_user[0], $this->smtp_pass[0]);

        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Initialize the Email Data
     *
     * @param   bool
     * @return  CI_Email
     */
    public function clear($clear_attachments = false)
    {
        $this->_subject     = '';
        $this->_body        = '';
        $this->_finalbody   = '';
        $this->_header_str  = '';
        $this->_replyto_flag    = false;
        $this->_recipients  = array();
        $this->_cc_array    = array();
        $this->_bcc_array   = array();
        $this->_headers     = array();
        $this->_debug_msg   = array();

        $this->set_header('Date', $this->_set_date());

        if ($clear_attachments !== false) {
            $this->_attachments = array();
        }

        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Set FROM
     *
     * @param   string  $from
     * @param   string  $name
     * @param   string  $return_path = NULL Return-Path
     * @return  CI_Email
     */
    public function from($from, $name = '', $return_path = null)
    {
        if (preg_match('/\<(.*)\>/', $from, $match)) {
            $from = $match[1];
        }

        if ($this->validate) {
            $this->validate_email($this->_str_to_array($from));
            if ($return_path) {
                $this->validate_email($this->_str_to_array($return_path));
            }
        }

        // prepare the display name
        if ($name !== '') {
            // only use Q encoding if there are characters that would require it
            if (! preg_match('/[\200-\377]/', $name)) {
                // add slashes for non-printing characters, slashes, and double quotes, and surround it in double quotes
                $name = '"' . addcslashes($name, "\0..\37\177'\"\\") . '"';
            } else {
                $name = $this->_prep_q_encoding($name);
            }
        }

        $this->set_header('From', $name . ' <' . $from . '>');

        isset($return_path) or $return_path = $from;
        $this->set_header('Return-Path', '<' . $return_path . '>');

        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Set Reply-to
     *
     * @param   string
     * @param   string
     * @return  CI_Email
     */
    public function reply_to($replyto, $name = '')
    {
        if (preg_match('/\<(.*)\>/', $replyto, $match)) {
            $replyto = $match[1];
        }

        if ($this->validate) {
            $this->validate_email($this->_str_to_array($replyto));
        }

        if ($name !== '') {
            // only use Q encoding if there are characters that would require it
            if (! preg_match('/[\200-\377]/', $name)) {
                // add slashes for non-printing characters, slashes, and double quotes, and surround it in double quotes
                $name = '"' . addcslashes($name, "\0..\37\177'\"\\") . '"';
            } else {
                $name = $this->_prep_q_encoding($name);
            }
        }

        $this->set_header('Reply-To', $name . ' <' . $replyto . '>');
        $this->_replyto_flag = true;

        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Set Recipients
     *
     * @param   string
     * @return  CI_Email
     */
    public function to($to)
    {
        $to = $this->_str_to_array($to);
        $to = $this->clean_email($to);

        if ($this->validate) {
            $this->validate_email($to);
        }

        if ($this->_get_protocol() !== 'mail') {
            $this->set_header('To', implode(', ', $to));
        }

        $this->_recipients = $to;

        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Set CC
     *
     * @param   string
     * @return  CI_Email
     */
    public function cc($cc)
    {
        $cc = $this->clean_email($this->_str_to_array($cc));

        if ($this->validate) {
            $this->validate_email($cc);
        }

        $this->set_header('Cc', implode(', ', $cc));

        if ($this->_get_protocol() === 'smtp') {
            $this->_cc_array = $cc;
        }

        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Set BCC
     *
     * @param   string
     * @param   string
     * @return  CI_Email
     */
    public function bcc($bcc, $limit = '')
    {
        if ($limit !== '' && is_numeric($limit)) {
            $this->bcc_batch_mode = true;
            $this->bcc_batch_size = $limit;
        }

        $bcc = $this->clean_email($this->_str_to_array($bcc));

        if ($this->validate) {
            $this->validate_email($bcc);
        }

        if ($this->_get_protocol() === 'smtp' or ($this->bcc_batch_mode && count($bcc) > $this->bcc_batch_size)) {
            $this->_bcc_array = $bcc;
        } else {
            $this->set_header('Bcc', implode(', ', $bcc));
        }

        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Set Email Subject
     *
     * @param   string
     * @return  CI_Email
     */
    public function subject($subject)
    {
        $subject = $this->_prep_q_encoding($subject);
        $this->set_header('Subject', $subject);
        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Set Body
     *
     * @param   string
     * @return  CI_Email
     */
    public function message($body)
    {
        $this->_body = rtrim(str_replace("\r", '', $body));

        /* strip slashes only if magic quotes is ON
           if we do it with magic quotes OFF, it strips real, user-inputted chars.

           NOTE: In PHP 5.4 get_magic_quotes_gpc() will always return 0 and
             it will probably not exist in future versions at all.
        */
        if (! is_php('5.4') && get_magic_quotes_gpc()) {
            $this->_body = stripslashes($this->_body);
        }

        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Assign file attachments
     *
     * @param   string  $file   Can be local path, URL or buffered content
     * @param   string  $disposition = 'attachment'
     * @param   string  $newname = NULL
     * @param   string  $mime = ''
     * @return  CI_Email
     */
    public function attach($file, $disposition = '', $newname = null, $mime = '')
    {
        if ($mime === '') {
            if (strpos($file, '://') === false && ! file_exists($file)) {
                $this->_set_error_message('lang:email_attachment_missing', $file);
                return false;
            }

            if (! $fp = @fopen($file, 'rb')) {
                $this->_set_error_message('lang:email_attachment_unreadable', $file);
                return false;
            }

            $file_content = stream_get_contents($fp);
            $mime = $this->_mime_types(pathinfo($file, PATHINFO_EXTENSION));
            fclose($fp);
        } else {
            $file_content = & $file; // buffered file
        }

        $this->_attachments[] = array(
            'name'      => array($file, $newname),
            'disposition'   => empty($disposition) ? 'attachment' : $disposition,  // Can also be 'inline'  Not sure if it matters
            'type'      => $mime,
            'content'   => chunk_split(base64_encode($file_content)),
            'multipart' => 'mixed'
        );

        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Set and return attachment Content-ID
     *
     * Useful for attached inline pictures
     *
     * @param   string  $filename
     * @return  string
     */
    public function attachment_cid($filename)
    {
        for ($i = 0, $c = count($this->_attachments); $i < $c; $i++) {
            if ($this->_attachments[$i]['name'][0] === $filename) {
                $this->_attachments[$i]['multipart'] = 'related';
                $this->_attachments[$i]['cid'] = uniqid(basename($this->_attachments[$i]['name'][0]) . '@');
                return $this->_attachments[$i]['cid'];
            }
        }

        return false;
    }

    // --------------------------------------------------------------------

    /**
     * Add a Header Item
     *
     * @param   string
     * @param   string
     * @return  CI_Email
     */
    public function set_header($header, $value)
    {
        $this->_headers[$header] = str_replace(array("\n", "\r"), '', $value);
        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Convert a String to an Array
     *
     * @param   string
     * @return  array
     */
    protected function _str_to_array($email)
    {
        if (! is_array($email)) {
            return (strpos($email, ',') !== false)
                ? preg_split('/[\s,]/', $email, -1, PREG_SPLIT_NO_EMPTY)
                : (array) trim($email);
        }

        return $email;
    }

    // --------------------------------------------------------------------

    /**
     * Set Multipart Value
     *
     * @param   string
     * @return  CI_Email
     */
    public function set_alt_message($str)
    {
        $this->alt_message = (string) $str;
        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Set Mailtype
     *
     * @param   string
     * @return  CI_Email
     */
    public function set_mailtype($type = 'text')
    {
        $this->mailtype = ($type === 'html') ? 'html' : 'text';
        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Set Wordwrap
     *
     * @param   bool
     * @return  CI_Email
     */
    public function set_wordwrap($wordwrap = true)
    {
        $this->wordwrap = (bool) $wordwrap;
        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Set Protocol
     *
     * @param   string
     * @return  CI_Email
     */
    public function set_protocol($protocol = 'mail')
    {
        $this->protocol = in_array($protocol, $this->_protocols, true) ? strtolower($protocol) : 'mail';
        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Set Priority
     *
     * @param   int
     * @return  CI_Email
     */
    public function set_priority($n = 3)
    {
        $this->priority = preg_match('/^[1-5]$/', $n) ? (int) $n : 3;
        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Set Newline Character
     *
     * @param   string
     * @return  CI_Email
     */
    public function set_newline($newline = "\n")
    {
        $this->newline = in_array($newline, array("\n", "\r\n", "\r")) ? $newline : "\n";
        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Set CRLF
     *
     * @param   string
     * @return  CI_Email
     */
    public function set_crlf($crlf = "\n")
    {
        $this->crlf = ($crlf !== "\n" && $crlf !== "\r\n" && $crlf !== "\r") ? "\n" : $crlf;
        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Get the Message ID
     *
     * @return  string
     */
    protected function _get_message_id()
    {
        $from = str_replace(array('>', '<'), '', $this->_headers['Return-Path']);
        return '<' . uniqid('') . strstr($from, '@') . '>';
    }

    // --------------------------------------------------------------------

    /**
     * Get Mail Protocol
     *
     * @return  mixed
     */
    protected function _get_protocol()
    {
        $this->protocol = strtolower($this->protocol);
        in_array($this->protocol, $this->_protocols, true) or $this->protocol = 'mail';
        return $this->protocol;
    }

    // --------------------------------------------------------------------

    /**
     * Get Mail Encoding
     *
     * @return  string
     */
    protected function _get_encoding()
    {
        in_array($this->_encoding, $this->_bit_depths) or $this->_encoding = '8bit';

        foreach ($this->_base_charsets as $charset) {
            if (strpos($this->charset, $charset) === 0) {
                $this->_encoding = '7bit';
            }
        }

        return $this->_encoding;
    }

    // --------------------------------------------------------------------

    /**
     * Get content type (text/html/attachment)
     *
     * @return  string
     */
    protected function _get_content_type()
    {
        if ($this->mailtype === 'html') {
            return empty($this->_attachments) ? 'html' : 'html-attach';
        } elseif ($this->mailtype === 'text' && ! empty($this->_attachments)) {
            return 'plain-attach';
        }

        return 'plain';
    }

    // --------------------------------------------------------------------

    /**
     * Set RFC 822 Date
     *
     * @return  string
     */
    protected function _set_date()
    {
        $timezone = date('Z');
        $operator = ($timezone[0] === '-') ? '-' : '+';
        $timezone = abs($timezone);
        $timezone = floor($timezone / 3600) * 100 + ($timezone % 3600) / 60;

        return sprintf('%s %s%04d', date('D, j M Y H:i:s'), $operator, $timezone);
    }

    // --------------------------------------------------------------------

    /**
     * Mime message
     *
     * @return  string
     */
    protected function _get_mime_message()
    {
        return 'This is a multi-part message in MIME format.' . $this->newline . 'Your email application may not support this format.';
    }

    // --------------------------------------------------------------------

    /**
     * Validate Email Address
     *
     * @param   string
     * @return  bool
     */
    public function validate_email($email)
    {
        if (! is_array($email)) {
            $this->_set_error_message('lang:email_must_be_array');
            return false;
        }

        foreach ($email as $val) {
            if (! $this->valid_email($val)) {
                $this->_set_error_message('lang:email_invalid_address', $val);
                return false;
            }
        }

        return true;
    }

    // --------------------------------------------------------------------

    /**
     * Email Validation
     *
     * @param   string
     * @return  bool
     */
    public function valid_email($email)
    {
        if (function_exists('idn_to_ascii') && strpos($email, '@')) {
            list($account, $domain) = explode('@', $email, 2);
            $domain = defined('INTL_IDNA_VARIANT_UTS46')
                ? idn_to_ascii($domain, 0, INTL_IDNA_VARIANT_UTS46)
                : idn_to_ascii($domain);

            if ($domain !== false) {
                $email = $account . '@' . $domain;
            }
        }

        return (bool) filter_var($email, FILTER_VALIDATE_EMAIL);
    }

    // --------------------------------------------------------------------

    /**
     * Clean Extended Email Address: Joe Smith <joe@smith.com>
     *
     * @param   string
     * @return  string
     */
    public function clean_email($email)
    {
        if (! is_array($email)) {
            return preg_match('/\<(.*)\>/', $email, $match) ? $match[1] : $email;
        }

        $clean_email = array();

        foreach ($email as $addy) {
            $clean_email[] = preg_match('/\<(.*)\>/', $addy, $match) ? $match[1] : $addy;
        }

        return $clean_email;
    }

    // --------------------------------------------------------------------

    /**
     * Build alternative plain text message
     *
     * Provides the raw message for use in plain-text headers of
     * HTML-formatted emails.
     * If the user hasn't specified his own alternative message
     * it creates one by stripping the HTML
     *
     * @return  string
     */
    protected function _get_alt_message()
    {
        if (! empty($this->alt_message)) {
            return ($this->wordwrap)
                ? $this->word_wrap($this->alt_message, 76)
                : $this->alt_message;
        }

        $body = preg_match('/\<body.*?\>(.*)\<\/body\>/si', $this->_body, $match) ? $match[1] : $this->_body;
        $body = str_replace("\t", '', preg_replace('#<!--(.*)--\>#', '', trim(strip_tags($body))));

        for ($i = 20; $i >= 3; $i--) {
            $body = str_replace(str_repeat("\n", $i), "\n\n", $body);
        }

        // Reduce multiple spaces
        $body = preg_replace('| +|', ' ', $body);

        return ($this->wordwrap)
            ? $this->word_wrap($body, 76)
            : $body;
    }

    // --------------------------------------------------------------------

    /**
     * Word Wrap
     *
     * @param   string
     * @param   int line-length limit
     * @return  string
     */
    public function word_wrap($str, $charlim = null)
    {
        // Set the character limit, if not already present
        if (empty($charlim)) {
            $charlim = empty($this->wrapchars) ? 76 : $this->wrapchars;
        }

        // Standardize newlines
        if (strpos($str, "\r") !== false) {
            $str = str_replace(array("\r\n", "\r"), "\n", $str);
        }

        // Reduce multiple spaces at end of line
        $str = preg_replace('| +\n|', "\n", $str);

        // If the current word is surrounded by {unwrap} tags we'll
        // strip the entire chunk and replace it with a marker.
        $unwrap = array();
        if (preg_match_all('|\{unwrap\}(.+?)\{/unwrap\}|s', $str, $matches)) {
            for ($i = 0, $c = count($matches[0]); $i < $c; $i++) {
                $unwrap[] = $matches[1][$i];
                $str = str_replace($matches[0][$i], '{{unwrapped' . $i . '}}', $str);
            }
        }

        // Use PHP's native function to do the initial wordwrap.
        // We set the cut flag to FALSE so that any individual words that are
        // too long get left alone. In the next step we'll deal with them.
        $str = wordwrap($str, $charlim, "\n", false);

        // Split the string into individual lines of text and cycle through them
        $output = '';
        foreach (explode("\n", $str) as $line) {
            // Is the line within the allowed character count?
            // If so we'll join it to the output and continue
            if (self::strlen($line) <= $charlim) {
                $output .= $line . $this->newline;
                continue;
            }

            $temp = '';
            do {
                // If the over-length word is a URL we won't wrap it
                if (preg_match('!\[url.+\]|://|www\.!', $line)) {
                    break;
                }

                // Trim the word down
                $temp .= self::substr($line, 0, $charlim - 1);
                $line = self::substr($line, $charlim - 1);
            } while (self::strlen($line) > $charlim);

            // If $temp contains data it means we had to split up an over-length
            // word into smaller chunks so we'll add it back to our current line
            if ($temp !== '') {
                $output .= $temp . $this->newline;
            }

            $output .= $line . $this->newline;
        }

        // Put our markers back
        if (count($unwrap) > 0) {
            foreach ($unwrap as $key => $val) {
                $output = str_replace('{{unwrapped' . $key . '}}', $val, $output);
            }
        }

        return $output;
    }

    // --------------------------------------------------------------------

    /**
     * Build final headers
     *
     * @return  void
     */
    protected function _build_headers()
    {
        $this->set_header('User-Agent', $this->useragent);
        $this->set_header('X-Sender', $this->clean_email($this->_headers['From']));
        $this->set_header('X-Mailer', $this->useragent);
        $this->set_header('X-Priority', $this->_priorities[$this->priority]);
        $this->set_header('Message-ID', $this->_get_message_id());
        $this->set_header('Mime-Version', '1.0');
    }

    // --------------------------------------------------------------------

    /**
     * Write Headers as a string
     *
     * @return  void
     */
    protected function _write_headers()
    {
        if ($this->protocol === 'mail') {
            if (isset($this->_headers['Subject'])) {
                $this->_subject = $this->_headers['Subject'];
                unset($this->_headers['Subject']);
            }
        }

        reset($this->_headers);
        $this->_header_str = '';

        foreach ($this->_headers as $key => $val) {
            $val = trim($val);

            if ($val !== '') {
                $this->_header_str .= $key . ': ' . $val . $this->newline;
            }
        }

        if ($this->_get_protocol() === 'mail') {
            $this->_header_str = rtrim($this->_header_str);
        }
    }

    // --------------------------------------------------------------------

    /**
     * Build Final Body and attachments
     *
     * @return  bool
     */
    protected function _build_message()
    {
        if ($this->wordwrap === true && $this->mailtype !== 'html') {
            $this->_body = $this->word_wrap($this->_body);
        }

        $this->_write_headers();

        $hdr = ($this->_get_protocol() === 'mail') ? $this->newline : '';
        $body = '';

        switch ($this->_get_content_type()) {
            case 'plain':
                $hdr .= 'Content-Type: text/plain; charset=' . $this->charset . $this->newline
                    . 'Content-Transfer-Encoding: ' . $this->_get_encoding();

                if ($this->_get_protocol() === 'mail') {
                    $this->_header_str .= $hdr;
                    $this->_finalbody = $this->_body;
                } else {
                    $this->_finalbody = $hdr . $this->newline . $this->newline . $this->_body;
                }

                return;

            case 'html':
                if ($this->send_multipart === false) {
                    $hdr .= 'Content-Type: text/html; charset=' . $this->charset . $this->newline
                        . 'Content-Transfer-Encoding: quoted-printable';
                } else {
                    $boundary = uniqid('B_ALT_');
                    $hdr .= 'Content-Type: multipart/alternative; boundary="' . $boundary . '"';

                    $body .= $this->_get_mime_message() . $this->newline . $this->newline
                        . '--' . $boundary . $this->newline

                        . 'Content-Type: text/plain; charset=' . $this->charset . $this->newline
                        . 'Content-Transfer-Encoding: ' . $this->_get_encoding() . $this->newline . $this->newline
                        . $this->_get_alt_message() . $this->newline . $this->newline
                        . '--' . $boundary . $this->newline

                        . 'Content-Type: text/html; charset=' . $this->charset . $this->newline
                        . 'Content-Transfer-Encoding: quoted-printable' . $this->newline . $this->newline;
                }

                $this->_finalbody = $body . $this->_prep_quoted_printable($this->_body) . $this->newline . $this->newline;

                if ($this->_get_protocol() === 'mail') {
                    $this->_header_str .= $hdr;
                } else {
                    $this->_finalbody = $hdr . $this->newline . $this->newline . $this->_finalbody;
                }

                if ($this->send_multipart !== false) {
                    $this->_finalbody .= '--' . $boundary . '--';
                }

                return;

            case 'plain-attach':
                $boundary = uniqid('B_ATC_');
                $hdr .= 'Content-Type: multipart/mixed; boundary="' . $boundary . '"';

                if ($this->_get_protocol() === 'mail') {
                    $this->_header_str .= $hdr;
                }

                $body .= $this->_get_mime_message() . $this->newline
                    . $this->newline
                    . '--' . $boundary . $this->newline
                    . 'Content-Type: text/plain; charset=' . $this->charset . $this->newline
                    . 'Content-Transfer-Encoding: ' . $this->_get_encoding() . $this->newline
                    . $this->newline
                    . $this->_body . $this->newline . $this->newline;

                $this->_append_attachments($body, $boundary);

                break;
            case 'html-attach':
                $alt_boundary = uniqid('B_ALT_');
                $last_boundary = null;

                if ($this->_attachments_have_multipart('mixed')) {
                    $atc_boundary = uniqid('B_ATC_');
                    $hdr .= 'Content-Type: multipart/mixed; boundary="' . $atc_boundary . '"';
                    $last_boundary = $atc_boundary;
                }

                if ($this->_attachments_have_multipart('related')) {
                    $rel_boundary = uniqid('B_REL_');
                    $rel_boundary_header = 'Content-Type: multipart/related; boundary="' . $rel_boundary . '"';

                    if (isset($last_boundary)) {
                        $body .= '--' . $last_boundary . $this->newline . $rel_boundary_header;
                    } else {
                        $hdr .= $rel_boundary_header;
                    }

                    $last_boundary = $rel_boundary;
                }

                if ($this->_get_protocol() === 'mail') {
                    $this->_header_str .= $hdr;
                }

                self::strlen($body) && $body .= $this->newline . $this->newline;
                $body .= $this->_get_mime_message() . $this->newline . $this->newline
                    . '--' . $last_boundary . $this->newline

                    . 'Content-Type: multipart/alternative; boundary="' . $alt_boundary . '"' . $this->newline . $this->newline
                    . '--' . $alt_boundary . $this->newline

                    . 'Content-Type: text/plain; charset=' . $this->charset . $this->newline
                    . 'Content-Transfer-Encoding: ' . $this->_get_encoding() . $this->newline . $this->newline
                    . $this->_get_alt_message() . $this->newline . $this->newline
                    . '--' . $alt_boundary . $this->newline

                    . 'Content-Type: text/html; charset=' . $this->charset . $this->newline
                    . 'Content-Transfer-Encoding: quoted-printable' . $this->newline . $this->newline

                    . $this->_prep_quoted_printable($this->_body) . $this->newline . $this->newline
                    . '--' . $alt_boundary . '--' . $this->newline . $this->newline;

                if (! empty($rel_boundary)) {
                    $body .= $this->newline . $this->newline;
                    $this->_append_attachments($body, $rel_boundary, 'related');
                }

                // multipart/mixed attachments
                if (! empty($atc_boundary)) {
                    $body .= $this->newline . $this->newline;
                    $this->_append_attachments($body, $atc_boundary, 'mixed');
                }

                break;
        }

        $this->_finalbody = ($this->_get_protocol() === 'mail')
            ? $body
            : $hdr . $this->newline . $this->newline . $body;

        return true;
    }

    // --------------------------------------------------------------------

    protected function _attachments_have_multipart($type)
    {
        foreach ($this->_attachments as &$attachment) {
            if ($attachment['multipart'] === $type) {
                return true;
            }
        }

        return false;
    }

    // --------------------------------------------------------------------

    /**
     * Prepares attachment string
     *
     * @param   string  $body       Message body to append to
     * @param   string  $boundary   Multipart boundary
     * @param   string  $multipart  When provided, only attachments of this type will be processed
     * @return  string
     */
    protected function _append_attachments(&$body, $boundary, $multipart = null)
    {
        for ($i = 0, $c = count($this->_attachments); $i < $c; $i++) {
            if (isset($multipart) && $this->_attachments[$i]['multipart'] !== $multipart) {
                continue;
            }

            $name = isset($this->_attachments[$i]['name'][1])
                ? $this->_attachments[$i]['name'][1]
                : basename($this->_attachments[$i]['name'][0]);

            $body .= '--' . $boundary . $this->newline
                . 'Content-Type: ' . $this->_attachments[$i]['type'] . '; name="' . $name . '"' . $this->newline
                . 'Content-Disposition: ' . $this->_attachments[$i]['disposition'] . ';' . $this->newline
                . 'Content-Transfer-Encoding: base64' . $this->newline
                . (empty($this->_attachments[$i]['cid']) ? '' : 'Content-ID: <' . $this->_attachments[$i]['cid'] . '>' . $this->newline)
                . $this->newline
                . $this->_attachments[$i]['content'] . $this->newline;
        }

        // $name won't be set if no attachments were appended,
        // and therefore a boundary wouldn't be necessary
        empty($name) or $body .= '--' . $boundary . '--';
    }

    // --------------------------------------------------------------------

    /**
     * Prep Quoted Printable
     *
     * Prepares string for Quoted-Printable Content-Transfer-Encoding
     * Refer to RFC 2045 http://www.ietf.org/rfc/rfc2045.txt
     *
     * @param   string
     * @return  string
     */
    protected function _prep_quoted_printable($str)
    {
        // ASCII code numbers for "safe" characters that can always be
        // used literally, without encoding, as described in RFC 2049.
        // http://www.ietf.org/rfc/rfc2049.txt
        static $ascii_safe_chars = array(
            // ' (  )   +   ,   -   .   /   :   =   ?
            39, 40, 41, 43, 44, 45, 46, 47, 58, 61, 63,
            // numbers
            48, 49, 50, 51, 52, 53, 54, 55, 56, 57,
            // upper-case letters
            65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90,
            // lower-case letters
            97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122
        );

        // We are intentionally wrapping so mail servers will encode characters
        // properly and MUAs will behave, so {unwrap} must go!
        $str = str_replace(array('{unwrap}', '{/unwrap}'), '', $str);

        // RFC 2045 specifies CRLF as "\r\n".
        // However, many developers choose to override that and violate
        // the RFC rules due to (apparently) a bug in MS Exchange,
        // which only works with "\n".
        if ($this->crlf === "\r\n") {
            return quoted_printable_encode($str);
        }

        // Reduce multiple spaces & remove nulls
        $str = preg_replace(array('| +|', '/\x00+/'), array(' ', ''), $str);

        // Standardize newlines
        if (strpos($str, "\r") !== false) {
            $str = str_replace(array("\r\n", "\r"), "\n", $str);
        }

        $escape = '=';
        $output = '';

        foreach (explode("\n", $str) as $line) {
            $length = self::strlen($line);
            $temp = '';

            // Loop through each character in the line to add soft-wrap
            // characters at the end of a line " =\r\n" and add the newly
            // processed line(s) to the output (see comment on $crlf class property)
            for ($i = 0; $i < $length; $i++) {
                // Grab the next character
                $char = $line[$i];
                $ascii = ord($char);

                // Convert spaces and tabs but only if it's the end of the line
                if ($ascii === 32 or $ascii === 9) {
                    if ($i === ($length - 1)) {
                        $char = $escape . sprintf('%02s', dechex($ascii));
                    }
                }
                // DO NOT move this below the $ascii_safe_chars line!
                //
                // = (equals) signs are allowed by RFC2049, but must be encoded
                // as they are the encoding delimiter!
                elseif ($ascii === 61) {
                    $char = $escape . strtoupper(sprintf('%02s', dechex($ascii)));  // =3D
                } elseif (! in_array($ascii, $ascii_safe_chars, true)) {
                    $char = $escape . strtoupper(sprintf('%02s', dechex($ascii)));
                }

                // If we're at the character limit, add the line to the output,
                // reset our temp variable, and keep on chuggin'
                if ((self::strlen($temp) + self::strlen($char)) >= 76) {
                    $output .= $temp . $escape . $this->crlf;
                    $temp = '';
                }

                // Add the character to our temporary line
                $temp .= $char;
            }

            // Add our completed line to the output
            $output .= $temp . $this->crlf;
        }

        // get rid of extra CRLF tacked onto the end
        return self::substr($output, 0, self::strlen($this->crlf) * -1);
    }

    // --------------------------------------------------------------------

    /**
     * Prep Q Encoding
     *
     * Performs "Q Encoding" on a string for use in email headers.
     * It's related but not identical to quoted-printable, so it has its
     * own method.
     *
     * @param   string
     * @return  string
     */
    protected function _prep_q_encoding($str)
    {
        $str = str_replace(array("\r", "\n"), '', $str);

        if ($this->charset === 'UTF-8') {
            // Note: We used to have mb_encode_mimeheader() as the first choice
            //       here, but it turned out to be buggy and unreliable. DO NOT
            //       re-add it! -- Narf
            if (ICONV_ENABLED === true) {
                $output = @iconv_mime_encode(
                    '',
                    $str,
                    array(
                        'scheme' => 'Q',
                        'line-length' => 76,
                        'input-charset' => $this->charset,
                        'output-charset' => $this->charset,
                        'line-break-chars' => $this->crlf
                    )
                );

                // There are reports that iconv_mime_encode() might fail and return FALSE
                if ($output !== false) {
                    // iconv_mime_encode() will always put a header field name.
                    // We've passed it an empty one, but it still prepends our
                    // encoded string with ': ', so we need to strip it.
                    return self::substr($output, 2);
                }

                $chars = iconv_strlen($str, 'UTF-8');
            } elseif (MB_ENABLED === true) {
                $chars = mb_strlen($str, 'UTF-8');
            }
        }

        // We might already have this set for UTF-8
        isset($chars) or $chars = self::strlen($str);

        $output = '=?' . $this->charset . '?Q?';
        for ($i = 0, $length = self::strlen($output); $i < $chars; $i++) {
            $chr = ($this->charset === 'UTF-8' && ICONV_ENABLED === true)
                ? '=' . implode('=', str_split(strtoupper(bin2hex(iconv_substr($str, $i, 1, $this->charset))), 2))
                : '=' . strtoupper(bin2hex($str[$i]));

            // RFC 2045 sets a limit of 76 characters per line.
            // We'll append ?= to the end of each line though.
            if ($length + ($l = self::strlen($chr)) > 74) {
                $output .= '?=' . $this->crlf // EOL
                    . ' =?' . $this->charset . '?Q?' . $chr; // New line
                $length = 6 + self::strlen($this->charset) + $l; // Reset the length for the new line
            } else {
                $output .= $chr;
                $length += $l;
            }
        }

        // End the header
        return $output . '?=';
    }

    // --------------------------------------------------------------------

    /**
     * Send Email
     *
     * @param   bool    $auto_clear = TRUE
     * @return  bool
     */
    public function send($auto_clear = true)
    {
        if (! isset($this->_headers['From'])) {
            $this->_set_error_message('lang:email_no_from');
            return false;
        }

        if ($this->_replyto_flag === false) {
            $this->reply_to($this->_headers['From']);
        }

        if (
            ! isset($this->_recipients) && ! isset($this->_headers['To'])
            && ! isset($this->_bcc_array) && ! isset($this->_headers['Bcc'])
            && ! isset($this->_headers['Cc'])
        ) {
            $this->_set_error_message('lang:email_no_recipients');
            return false;
        }

        $this->_build_headers();

        if ($this->bcc_batch_mode && count($this->_bcc_array) > $this->bcc_batch_size) {
            $result = $this->batch_bcc_send();

            if ($result && $auto_clear) {
                $this->clear();
            }

            return $result;
        }

        if ($this->_build_message() === false) {
            return false;
        }

        $result = $this->_spool_email();

        if ($result && $auto_clear) {
            $this->clear();
        }

        return $result;
    }

    // --------------------------------------------------------------------

    /**
     * Batch Bcc Send. Sends groups of BCCs in batches
     *
     * @return  void
     */
    public function batch_bcc_send()
    {
        $float = $this->bcc_batch_size - 1;
        $set = '';
        $chunk = array();

        for ($i = 0, $c = count($this->_bcc_array); $i < $c; $i++) {
            if (isset($this->_bcc_array[$i])) {
                $set .= ', ' . $this->_bcc_array[$i];
            }

            if ($i === $float) {
                $chunk[] = self::substr($set, 1);
                $float += $this->bcc_batch_size;
                $set = '';
            }

            if ($i === $c - 1) {
                $chunk[] = self::substr($set, 1);
            }
        }

        for ($i = 0, $c = count($chunk); $i < $c; $i++) {
            unset($this->_headers['Bcc']);

            $bcc = $this->clean_email($this->_str_to_array($chunk[$i]));

            if ($this->protocol !== 'smtp') {
                $this->set_header('Bcc', implode(', ', $bcc));
            } else {
                $this->_bcc_array = $bcc;
            }

            if ($this->_build_message() === false) {
                return false;
            }

            $this->_spool_email();
        }
    }

    // --------------------------------------------------------------------

    /**
     * Unwrap special elements
     *
     * @return  void
     */
    protected function _unwrap_specials()
    {
        $this->_finalbody = preg_replace_callback('/\{unwrap\}(.*?)\{\/unwrap\}/si', array($this, '_remove_nl_callback'), $this->_finalbody);
    }

    // --------------------------------------------------------------------

    /**
     * Strip line-breaks via callback
     *
     * @param   string  $matches
     * @return  string
     */
    protected function _remove_nl_callback($matches)
    {
        if (strpos($matches[1], "\r") !== false or strpos($matches[1], "\n") !== false) {
            $matches[1] = str_replace(array("\r\n", "\r", "\n"), '', $matches[1]);
        }

        return $matches[1];
    }

    // --------------------------------------------------------------------

    /**
     * Spool mail to the mail server
     *
     * @return  bool
     */
    protected function _spool_email()
    {
        $this->_unwrap_specials();

        $protocol = $this->_get_protocol();
        $method   = '_send_with_' . $protocol;
        if (! $this->$method()) {
            $this->_set_error_message('lang:email_send_failure_' . ($protocol === 'mail' ? 'phpmail' : $protocol));
            return false;
        }

        $this->_set_error_message('lang:email_sent', $protocol);
        return true;
    }

    // --------------------------------------------------------------------

    /**
     * Validate email for shell
     *
     * Applies stricter, shell-safe validation to email addresses.
     * Introduced to prevent RCE via sendmail's -f option.
     *
     * @see https://github.com/bcit-ci/CodeIgniter/issues/4963
     * @see https://gist.github.com/Zenexer/40d02da5e07f151adeaeeaa11af9ab36
     * @license https://creativecommons.org/publicdomain/zero/1.0/  CC0 1.0, Public Domain
     *
     * Credits for the base concept go to Paul Buonopane <paul@namepros.com>
     *
     * @param   string  $email
     * @return  bool
     */
    protected function _validate_email_for_shell(&$email)
    {
        if (function_exists('idn_to_ascii') && strpos($email, '@')) {
            list($account, $domain) = explode('@', $email, 2);
            $domain = defined('INTL_IDNA_VARIANT_UTS46')
                ? idn_to_ascii($domain, 0, INTL_IDNA_VARIANT_UTS46)
                : idn_to_ascii($domain);

            if ($domain !== false) {
                $email = $account . '@' . $domain;
            }
        }

        return (filter_var($email, FILTER_VALIDATE_EMAIL) === $email && preg_match('#\A[a-z0-9._+-]+@[a-z0-9.-]{1,253}\z#i', $email));
    }

    // --------------------------------------------------------------------

    /**
     * Send using mail()
     *
     * @return  bool
     */
    protected function _send_with_mail()
    {
        if (is_array($this->_recipients)) {
            $this->_recipients = implode(', ', $this->_recipients);
        }

        // _validate_email_for_shell() below accepts by reference,
        // so this needs to be assigned to a variable
        $from = $this->clean_email($this->_headers['Return-Path']);

        if ($this->_safe_mode === true || ! $this->_validate_email_for_shell($from)) {
            return mail($this->_recipients, $this->_subject, $this->_finalbody, $this->_header_str);
        } else {
            // most documentation of sendmail using the "-f" flag lacks a space after it, however
            // we've encountered servers that seem to require it to be in place.
            return mail($this->_recipients, $this->_subject, $this->_finalbody, $this->_header_str, '-f ' . $from);
        }
    }

    // --------------------------------------------------------------------

    /**
     * Send using Sendmail
     *
     * @return  bool
     */
    protected function _send_with_sendmail()
    {
        // _validate_email_for_shell() below accepts by reference,
        // so this needs to be assigned to a variable
        $from = $this->clean_email($this->_headers['From']);
        if ($this->_validate_email_for_shell($from)) {
            $from = '-f ' . $from;
        } else {
            $from = '';
        }

        // is popen() enabled?
        if (! function_usable('popen') or false === ($fp = @popen($this->mailpath . ' -oi ' . $from . ' -t', 'w'))) {
            // server probably has popen disabled, so nothing we can do to get a verbose error.
            return false;
        }

        fputs($fp, $this->_header_str);
        fputs($fp, $this->_finalbody);

        $status = pclose($fp);

        if ($status !== 0) {
            $this->_set_error_message('lang:email_exit_status', $status);
            $this->_set_error_message('lang:email_no_socket');
            return false;
        }

        return true;
    }

    // --------------------------------------------------------------------

    /**
     * Send using SMTP
     *
     * @return  bool
     */
    protected function _send_with_smtp()
    {
        if ($this->smtp_host === '') {
            $this->_set_error_message('lang:email_no_hostname');
            return false;
        }

        if (! $this->_smtp_connect() or ! $this->_smtp_authenticate()) {
            return false;
        }

        if (! $this->_send_command('from', $this->clean_email($this->_headers['From']))) {
            $this->_smtp_end();
            return false;
        }

        foreach ($this->_recipients as $val) {
            if (! $this->_send_command('to', $val)) {
                $this->_smtp_end();
                return false;
            }
        }

        if (count($this->_cc_array) > 0) {
            foreach ($this->_cc_array as $val) {
                if ($val !== '' && ! $this->_send_command('to', $val)) {
                    $this->_smtp_end();
                    return false;
                }
            }
        }

        if (count($this->_bcc_array) > 0) {
            foreach ($this->_bcc_array as $val) {
                if ($val !== '' && ! $this->_send_command('to', $val)) {
                    $this->_smtp_end();
                    return false;
                }
            }
        }

        if (! $this->_send_command('data')) {
            $this->_smtp_end();
            return false;
        }

        // perform dot transformation on any lines that begin with a dot
        $this->_send_data($this->_header_str . preg_replace('/^\./m', '..$1', $this->_finalbody));

        $this->_send_data('.');

        $reply = $this->_get_smtp_data();
        $this->_set_error_message($reply);

        $this->_smtp_end();

        if (strpos($reply, '250') !== 0) {
            $this->_set_error_message('lang:email_smtp_error', $reply);
            return false;
        }

        return true;
    }

    // --------------------------------------------------------------------

    /**
     * SMTP End
     *
     * Shortcut to send RSET or QUIT depending on keep-alive
     *
     * @return  void
     */
    protected function _smtp_end()
    {
        ($this->smtp_keepalive)
            ? $this->_send_command('reset')
            : $this->_send_command('quit');
    }

    // --------------------------------------------------------------------

    /**
     * SMTP Connect
     *
     * @return  string
     */
    protected function _smtp_connect()
    {
        if (is_resource($this->_smtp_connect)) {
            return true;
        }

        $ssl = ($this->smtp_crypto === 'ssl') ? 'ssl://' : '';

        $this->_smtp_connect = fsockopen(
            $ssl . $this->smtp_host,
            $this->smtp_port,
            $errno,
            $errstr,
            $this->smtp_timeout
        );

        if (! is_resource($this->_smtp_connect)) {
            $this->_set_error_message('lang:email_smtp_error', $errno . ' ' . $errstr);
            return false;
        }

        stream_set_timeout($this->_smtp_connect, $this->smtp_timeout);
        $this->_set_error_message($this->_get_smtp_data());

        if ($this->smtp_crypto === 'tls') {
            $this->_send_command('hello');
            $this->_send_command('starttls');

            /**
             * STREAM_CRYPTO_METHOD_TLS_CLIENT is quite the mess ...
             *
             * - On PHP <5.6 it doesn't even mean TLS, but SSL 2.0, and there's no option to use actual TLS
             * - On PHP 5.6.0-5.6.6, >=7.2 it means negotiation with any of TLS 1.0, 1.1, 1.2
             * - On PHP 5.6.7-7.1.* it means only TLS 1.0
             *
             * We want the negotiation, so we'll force it below ...
             */
            $method = is_php('5.6')
                ? STREAM_CRYPTO_METHOD_TLSv1_0_CLIENT | STREAM_CRYPTO_METHOD_TLSv1_1_CLIENT | STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT
                : STREAM_CRYPTO_METHOD_TLS_CLIENT;
            $crypto = stream_socket_enable_crypto($this->_smtp_connect, true, $method);

            if ($crypto !== true) {
                $this->_set_error_message('lang:email_smtp_error', $this->_get_smtp_data());
                return false;
            }
        }

        return $this->_send_command('hello');
    }

    // --------------------------------------------------------------------

    /**
     * Send SMTP command
     *
     * @param   string
     * @param   string
     * @return  bool
     */
    protected function _send_command($cmd, $data = '')
    {
        switch ($cmd) {
            case 'hello':
                if ($this->_smtp_auth or $this->_get_encoding() === '8bit') {
                    $this->_send_data('EHLO ' . $this->_get_hostname());
                } else {
                    $this->_send_data('HELO ' . $this->_get_hostname());
                }

                $resp = 250;
                break;
            case 'starttls':
                $this->_send_data('STARTTLS');
                $resp = 220;
                break;
            case 'from':
                $this->_send_data('MAIL FROM:<' . $data . '>');
                $resp = 250;
                break;
            case 'to':
                if ($this->dsn) {
                    $this->_send_data('RCPT TO:<' . $data . '> NOTIFY=SUCCESS,DELAY,FAILURE ORCPT=rfc822;' . $data);
                } else {
                    $this->_send_data('RCPT TO:<' . $data . '>');
                }

                $resp = 250;
                break;
            case 'data':
                $this->_send_data('DATA');
                $resp = 354;
                break;
            case 'reset':
                $this->_send_data('RSET');
                $resp = 250;
                break;
            case 'quit':
                $this->_send_data('QUIT');
                $resp = 221;
                break;
        }

        $reply = $this->_get_smtp_data();

        $this->_debug_msg[] = '<pre>' . $cmd . ': ' . $reply . '</pre>';

        if ((int) self::substr($reply, 0, 3) !== $resp) {
            $this->_set_error_message('lang:email_smtp_error', $reply);
            return false;
        }

        if ($cmd === 'quit') {
            fclose($this->_smtp_connect);
        }

        return true;
    }

    // --------------------------------------------------------------------

    /**
     * SMTP Authenticate
     *
     * @return  bool
     */
    protected function _smtp_authenticate()
    {
        if (! $this->_smtp_auth) {
            return true;
        }

        if ($this->smtp_user === '' && $this->smtp_pass === '') {
            $this->_set_error_message('lang:email_no_smtp_unpw');
            return false;
        }

        $this->_send_data('AUTH LOGIN');

        $reply = $this->_get_smtp_data();

        if (strpos($reply, '503') === 0) {    // Already authenticated
            return true;
        } elseif (strpos($reply, '334') !== 0) {
            $this->_set_error_message('lang:email_failed_smtp_login', $reply);
            return false;
        }

        $this->_send_data(base64_encode($this->smtp_user));

        $reply = $this->_get_smtp_data();

        if (strpos($reply, '334') !== 0) {
            $this->_set_error_message('lang:email_smtp_auth_un', $reply);
            return false;
        }

        $this->_send_data(base64_encode($this->smtp_pass));

        $reply = $this->_get_smtp_data();

        if (strpos($reply, '235') !== 0) {
            $this->_set_error_message('lang:email_smtp_auth_pw', $reply);
            return false;
        }

        if ($this->smtp_keepalive) {
            $this->_smtp_auth = false;
        }

        return true;
    }

    // --------------------------------------------------------------------

    /**
     * Send SMTP data
     *
     * @param   string  $data
     * @return  bool
     */
    protected function _send_data($data)
    {
        $data .= $this->newline;
        for ($written = $timestamp = 0, $length = self::strlen($data); $written < $length; $written += $result) {
            if (($result = fwrite($this->_smtp_connect, self::substr($data, $written))) === false) {
                break;
            }
            // See https://bugs.php.net/bug.php?id=39598 and http://php.net/manual/en/function.fwrite.php#96951
            elseif ($result === 0) {
                if ($timestamp === 0) {
                    $timestamp = time();
                } elseif ($timestamp < (time() - $this->smtp_timeout)) {
                    $result = false;
                    break;
                }

                usleep(250000);
                continue;
            }

            $timestamp = 0;
        }

        if ($result === false) {
            $this->_set_error_message('lang:email_smtp_data_failure', $data);
            return false;
        }

        return true;
    }

    // --------------------------------------------------------------------

    /**
     * Get SMTP data
     *
     * @return  string
     */
    protected function _get_smtp_data()
    {
        $data = '';

        while ($str = fgets($this->_smtp_connect, 512)) {
            $data .= $str;

            if ($str[3] === ' ') {
                break;
            }
        }

        return $data;
    }

    // --------------------------------------------------------------------

    /**
     * Get Hostname
     *
     * There are only two legal types of hostname - either a fully
     * qualified domain name (eg: "mail.example.com") or an IP literal
     * (eg: "[1.2.3.4]").
     *
     * @link    https://tools.ietf.org/html/rfc5321#section-2.3.5
     * @link    http://cbl.abuseat.org/namingproblems.html
     * @return  string
     */
    protected function _get_hostname()
    {
        if (isset($_SERVER['SERVER_NAME'])) {
            return $_SERVER['SERVER_NAME'];
        }

        return isset($_SERVER['SERVER_ADDR']) ? '[' . $_SERVER['SERVER_ADDR'] . ']' : '[127.0.0.1]';
    }

    // --------------------------------------------------------------------

    /**
     * Get Debug Message
     *
     * @param   array   $include    List of raw data chunks to include in the output
     *                  Valid options are: 'headers', 'subject', 'body'
     * @return  string
     */
    public function print_debugger($include = array('headers', 'subject', 'body'))
    {
        $msg = '';

        if (count($this->_debug_msg) > 0) {
            foreach ($this->_debug_msg as $val) {
                $msg .= $val;
            }
        }

        // Determine which parts of our raw data needs to be printed
        $raw_data = '';
        is_array($include) or $include = array($include);

        if (in_array('headers', $include, true)) {
            $raw_data = htmlspecialchars($this->_header_str) . "\n";
        }

        if (in_array('subject', $include, true)) {
            $raw_data .= htmlspecialchars($this->_subject) . "\n";
        }

        if (in_array('body', $include, true)) {
            $raw_data .= htmlspecialchars($this->_finalbody);
        }

        return $msg . ($raw_data === '' ? '' : '<pre>' . $raw_data . '</pre>');
    }

    // --------------------------------------------------------------------

    /**
     * Set Message
     *
     * @param   string  $msg
     * @param   string  $val = ''
     * @return  void
     */
    protected function _set_error_message($msg, $val = '')
    {
        $CI = & get_instance();
        $CI->lang->load('email');

        if (sscanf($msg, 'lang:%s', $line) !== 1 or false === ($line = $CI->lang->line($line))) {
            $this->_debug_msg[] = str_replace('%s', $val, $msg) . '<br />';
        } else {
            $this->_debug_msg[] = str_replace('%s', $val, $line) . '<br />';
        }
    }

    // --------------------------------------------------------------------

    /**
     * Mime Types
     *
     * @param   string
     * @return  string
     */
    protected function _mime_types($ext = '')
    {
        $ext = strtolower($ext);

        $mimes = & get_mimes();

        if (isset($mimes[$ext])) {
            return is_array($mimes[$ext])
                ? current($mimes[$ext])
                : $mimes[$ext];
        }

        return 'application/x-unknown-content-type';
    }

    // --------------------------------------------------------------------

    /**
     * Destructor
     *
     * @return  void
     */
    public function __destruct()
    {
        is_resource($this->_smtp_connect) && $this->_send_command('quit');
    }

    // --------------------------------------------------------------------

    /**
     * Byte-safe strlen()
     *
     * @param   string  $str
     * @return  int
     */
    protected static function strlen($str)
    {
        return (self::$func_overload)
            ? mb_strlen($str, '8bit')
            : strlen($str);
    }

    // --------------------------------------------------------------------

    /**
     * Byte-safe substr()
     *
     * @param   string  $str
     * @param   int $start
     * @param   int $length
     * @return  string
     */
    protected static function substr($str, $start, $length = null)
    {
        if (self::$func_overload) {
            // mb_substr($str, $start, null, '8bit') returns an empty
            // string on PHP 5.3
            isset($length) or $length = ($start >= 0 ? self::strlen($str) - $start : -$start);
            return mb_substr($str, $start, $length, '8bit');
        }

        return isset($length)
            ? substr($str, $start, $length)
            : substr($str, $start);
    }
}