Wordpress - Sending multipart (text/html) emails via wp_mail() will likely get your domain banned
The following version of wp_mail() is with the patch applied of @rmccue/@MattyRob in the ticket https://core.trac.wordpress.org/ticket/15448, refreshed for 4.2.2, which allows $message to be an array containing content-type keyed alternates:
/**
* Send mail, similar to PHP's mail
*
* A true return value does not automatically mean that the user received the
* email successfully. It just only means that the method used was able to
* process the request without any errors.
*
* Using the two 'wp_mail_from' and 'wp_mail_from_name' hooks allow from
* creating a from address like 'Name <[email protected]>' when both are set. If
* just 'wp_mail_from' is set, then just the email address will be used with no
* name.
*
* The default content type is 'text/plain' which does not allow using HTML.
* However, you can set the content type of the email by using the
* 'wp_mail_content_type' filter.
*
* If $message is an array, the key of each is used to add as an attachment
* with the value used as the body. The 'text/plain' element is used as the
* text version of the body, with the 'text/html' element used as the HTML
* version of the body. All other types are added as attachments.
*
* The default charset is based on the charset used on the blog. The charset can
* be set using the 'wp_mail_charset' filter.
*
* @since 1.2.1
*
* @uses PHPMailer
*
* @param string|array $to Array or comma-separated list of email addresses to send message.
* @param string $subject Email subject
* @param string|array $message Message contents
* @param string|array $headers Optional. Additional headers.
* @param string|array $attachments Optional. Files to attach.
* @return bool Whether the email contents were sent successfully.
*/
function wp_mail( $to, $subject, $message, $headers = '', $attachments = array() ) {
// Compact the input, apply the filters, and extract them back out
/**
* Filter the wp_mail() arguments.
*
* @since 2.2.0
*
* @param array $args A compacted array of wp_mail() arguments, including the "to" email,
* subject, message, headers, and attachments values.
*/
$atts = apply_filters( 'wp_mail', compact( 'to', 'subject', 'message', 'headers', 'attachments' ) );
if ( isset( $atts['to'] ) ) {
$to = $atts['to'];
}
if ( isset( $atts['subject'] ) ) {
$subject = $atts['subject'];
}
if ( isset( $atts['message'] ) ) {
$message = $atts['message'];
}
if ( isset( $atts['headers'] ) ) {
$headers = $atts['headers'];
}
if ( isset( $atts['attachments'] ) ) {
$attachments = $atts['attachments'];
}
if ( ! is_array( $attachments ) ) {
$attachments = explode( "\n", str_replace( "\r\n", "\n", $attachments ) );
}
global $phpmailer;
// (Re)create it, if it's gone missing
if ( ! ( $phpmailer instanceof PHPMailer ) ) {
require_once ABSPATH . WPINC . '/class-phpmailer.php';
require_once ABSPATH . WPINC . '/class-smtp.php';
$phpmailer = new PHPMailer( true );
}
// Headers
if ( empty( $headers ) ) {
$headers = array();
} else {
if ( !is_array( $headers ) ) {
// Explode the headers out, so this function can take both
// string headers and an array of headers.
$tempheaders = explode( "\n", str_replace( "\r\n", "\n", $headers ) );
} else {
$tempheaders = $headers;
}
$headers = array();
$cc = array();
$bcc = array();
// If it's actually got contents
if ( !empty( $tempheaders ) ) {
// Iterate through the raw headers
foreach ( (array) $tempheaders as $header ) {
if ( strpos($header, ':') === false ) {
if ( false !== stripos( $header, 'boundary=' ) ) {
$parts = preg_split('/boundary=/i', trim( $header ) );
$boundary = trim( str_replace( array( "'", '"' ), '', $parts[1] ) );
}
continue;
}
// Explode them out
list( $name, $content ) = explode( ':', trim( $header ), 2 );
// Cleanup crew
$name = trim( $name );
$content = trim( $content );
switch ( strtolower( $name ) ) {
// Mainly for legacy -- process a From: header if it's there
case 'from':
$bracket_pos = strpos( $content, '<' );
if ( $bracket_pos !== false ) {
// Text before the bracketed email is the "From" name.
if ( $bracket_pos > 0 ) {
$from_name = substr( $content, 0, $bracket_pos - 1 );
$from_name = str_replace( '"', '', $from_name );
$from_name = trim( $from_name );
}
$from_email = substr( $content, $bracket_pos + 1 );
$from_email = str_replace( '>', '', $from_email );
$from_email = trim( $from_email );
// Avoid setting an empty $from_email.
} elseif ( '' !== trim( $content ) ) {
$from_email = trim( $content );
}
break;
case 'content-type':
if ( is_array($message) ) {
// Multipart email, ignore the content-type header
break;
}
if ( strpos( $content, ';' ) !== false ) {
list( $type, $charset_content ) = explode( ';', $content );
$content_type = trim( $type );
if ( false !== stripos( $charset_content, 'charset=' ) ) {
$charset = trim( str_replace( array( 'charset=', '"' ), '', $charset_content ) );
} elseif ( false !== stripos( $charset_content, 'boundary=' ) ) {
$boundary = trim( str_replace( array( 'BOUNDARY=', 'boundary=', '"' ), '', $charset_content ) );
$charset = '';
}
// Avoid setting an empty $content_type.
} elseif ( '' !== trim( $content ) ) {
$content_type = trim( $content );
}
break;
case 'cc':
$cc = array_merge( (array) $cc, explode( ',', $content ) );
break;
case 'bcc':
$bcc = array_merge( (array) $bcc, explode( ',', $content ) );
break;
default:
// Add it to our grand headers array
$headers[trim( $name )] = trim( $content );
break;
}
}
}
}
// Empty out the values that may be set
$phpmailer->ClearAllRecipients();
$phpmailer->ClearAttachments();
$phpmailer->ClearCustomHeaders();
$phpmailer->ClearReplyTos();
$phpmailer->Body= '';
$phpmailer->AltBody= '';
// From email and name
// If we don't have a name from the input headers
if ( !isset( $from_name ) )
$from_name = 'WordPress';
/* If we don't have an email from the input headers default to wordpress@$sitename
* Some hosts will block outgoing mail from this address if it doesn't exist but
* there's no easy alternative. Defaulting to admin_email might appear to be another
* option but some hosts may refuse to relay mail from an unknown domain. See
* https://core.trac.wordpress.org/ticket/5007.
*/
if ( !isset( $from_email ) ) {
// Get the site domain and get rid of www.
$sitename = strtolower( $_SERVER['SERVER_NAME'] );
if ( substr( $sitename, 0, 4 ) == 'www.' ) {
$sitename = substr( $sitename, 4 );
}
$from_email = 'wordpress@' . $sitename;
}
/**
* Filter the email address to send from.
*
* @since 2.2.0
*
* @param string $from_email Email address to send from.
*/
$phpmailer->From = apply_filters( 'wp_mail_from', $from_email );
/**
* Filter the name to associate with the "from" email address.
*
* @since 2.3.0
*
* @param string $from_name Name associated with the "from" email address.
*/
$phpmailer->FromName = apply_filters( 'wp_mail_from_name', $from_name );
// Set destination addresses
if ( !is_array( $to ) )
$to = explode( ',', $to );
foreach ( (array) $to as $recipient ) {
try {
// Break $recipient into name and address parts if in the format "Foo <[email protected]>"
$recipient_name = '';
if( preg_match( '/(.*)<(.+)>/', $recipient, $matches ) ) {
if ( count( $matches ) == 3 ) {
$recipient_name = $matches[1];
$recipient = $matches[2];
}
}
$phpmailer->AddAddress( $recipient, $recipient_name);
} catch ( phpmailerException $e ) {
continue;
}
}
// If we don't have a charset from the input headers
if ( !isset( $charset ) )
$charset = get_bloginfo( 'charset' );
// Set the content-type and charset
/**
* Filter the default wp_mail() charset.
*
* @since 2.3.0
*
* @param string $charset Default email charset.
*/
$phpmailer->CharSet = apply_filters( 'wp_mail_charset', $charset );
// Set mail's subject and body
$phpmailer->Subject = $subject;
if ( is_string($message) ) {
$phpmailer->Body = $message;
// Set Content-Type and charset
// If we don't have a content-type from the input headers
if ( !isset( $content_type ) )
$content_type = 'text/plain';
/**
* Filter the wp_mail() content type.
*
* @since 2.3.0
*
* @param string $content_type Default wp_mail() content type.
*/
$content_type = apply_filters( 'wp_mail_content_type', $content_type );
$phpmailer->ContentType = $content_type;
// Set whether it's plaintext, depending on $content_type
if ( 'text/html' == $content_type )
$phpmailer->IsHTML( true );
// For backwards compatibility, new multipart emails should use
// the array style $message. This never really worked well anyway
if ( false !== stripos( $content_type, 'multipart' ) && ! empty($boundary) )
$phpmailer->AddCustomHeader( sprintf( "Content-Type: %s;\n\t boundary=\"%s\"", $content_type, $boundary ) );
}
elseif ( is_array($message) ) {
foreach ($message as $type => $bodies) {
foreach ((array) $bodies as $body) {
if ($type === 'text/html') {
$phpmailer->Body = $body;
}
elseif ($type === 'text/plain') {
$phpmailer->AltBody = $body;
}
else {
$phpmailer->AddAttachment($body, '', 'base64', $type);
}
}
}
}
// Add any CC and BCC recipients
if ( !empty( $cc ) ) {
foreach ( (array) $cc as $recipient ) {
try {
// Break $recipient into name and address parts if in the format "Foo <[email protected]>"
$recipient_name = '';
if( preg_match( '/(.*)<(.+)>/', $recipient, $matches ) ) {
if ( count( $matches ) == 3 ) {
$recipient_name = $matches[1];
$recipient = $matches[2];
}
}
$phpmailer->AddCc( $recipient, $recipient_name );
} catch ( phpmailerException $e ) {
continue;
}
}
}
if ( !empty( $bcc ) ) {
foreach ( (array) $bcc as $recipient) {
try {
// Break $recipient into name and address parts if in the format "Foo <[email protected]>"
$recipient_name = '';
if( preg_match( '/(.*)<(.+)>/', $recipient, $matches ) ) {
if ( count( $matches ) == 3 ) {
$recipient_name = $matches[1];
$recipient = $matches[2];
}
}
$phpmailer->AddBcc( $recipient, $recipient_name );
} catch ( phpmailerException $e ) {
continue;
}
}
}
// Set to use PHP's mail()
$phpmailer->IsMail();
// Set custom headers
if ( !empty( $headers ) ) {
foreach ( (array) $headers as $name => $content ) {
$phpmailer->AddCustomHeader( sprintf( '%1$s: %2$s', $name, $content ) );
}
}
if ( !empty( $attachments ) ) {
foreach ( $attachments as $attachment ) {
try {
$phpmailer->AddAttachment($attachment);
} catch ( phpmailerException $e ) {
continue;
}
}
}
/**
* Fires after PHPMailer is initialized.
*
* @since 2.2.0
*
* @param PHPMailer &$phpmailer The PHPMailer instance, passed by reference.
*/
do_action_ref_array( 'phpmailer_init', array( &$phpmailer ) );
// Send!
try {
return $phpmailer->Send();
} catch ( phpmailerException $e ) {
return false;
}
}
So if you put that in your eg "wp-content/mu-plugins/functions.php" file then it will override the WP version. It has a nice usage without any messing around with headers, eg:
// Set $to to an hotmail.com or outlook.com email
$to = "[email protected]";
$subject = 'wp_mail testing multipart';
$message['text/plain'] = 'Hello world! This is plain text...';
$message['text/html'] = '<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
</head>
<body>
<p>Hello World! This is HTML...</p>
</body>
</html>';
add_filter( 'wp_mail_from', $from_func = function ( $from_email ) { return '[email protected]'; } );
add_filter( 'wp_mail_from_name', $from_name_func = function ( $from_name ) { return 'Foo'; } );
// send email
wp_mail( $to, $subject, $message );
remove_filter( 'wp_mail_from', $from_func );
remove_filter( 'wp_mail_from_name', $from_name_func );
Please note I haven't tested this with actual emails...
TLDR, the simple solution is:
add_action('phpmailer_init','wp_mail_set_text_body');
function wp_mail_set_text_body($phpmailer) {
if (empty($phpmailer->AltBody)) {$phpmailer->AltBody = strip_tags($phpmailer->Body);}
}
Then you don't need to set the headers explicitly at all, the header boundaries are set correctly for you.
Read on to for a detailed explanation as to why...
This is not really a WordPress bug at all, it is a phpmailer one in not allowing for custom headers... if you look at class-phpmailer.php:
public function getMailMIME()
{
$result = '';
$ismultipart = true;
switch ($this->message_type) {
case 'inline':
$result .= $this->headerLine('Content-Type', 'multipart/related;');
$result .= $this->textLine("\tboundary=\"" . $this->boundary[1] . '"');
break;
case 'attach':
case 'inline_attach':
case 'alt_attach':
case 'alt_inline_attach':
$result .= $this->headerLine('Content-Type', 'multipart/mixed;');
$result .= $this->textLine("\tboundary=\"" . $this->boundary[1] . '"');
break;
case 'alt':
case 'alt_inline':
$result .= $this->headerLine('Content-Type', 'multipart/alternative;');
$result .= $this->textLine("\tboundary=\"" . $this->boundary[1] . '"');
break;
default:
// Catches case 'plain': and case '':
$result .= $this->textLine('Content-Type: ' . $this->ContentType . '; charset=' . $this->CharSet);
$ismultipart = false;
break;
}
You can see the offending default case is what is outputting the extra header line with charset and no boundary. Setting the content type by filter does not solve this by itself only because the alt case here is set on message_type by checking AltBody is not empty rather than the content type.
protected function setMessageType()
{
$type = array();
if ($this->alternativeExists()) {
$type[] = 'alt';
}
if ($this->inlineImageExists()) {
$type[] = 'inline';
}
if ($this->attachmentExists()) {
$type[] = 'attach';
}
$this->message_type = implode('_', $type);
if ($this->message_type == '') {
$this->message_type = 'plain';
}
}
public function alternativeExists()
{
return !empty($this->AltBody);
}
In the end what this means is as soon as you attach a file or inline image, or set the AltBody, the offending bug should be bypassed. It also means there is no need to explicitly set the content type because as soon as there is an AltBody it is set to multipart/alternative by phpmailer.
So the simple answer is:
add_action('phpmailer_init','wp_mail_set_text_body');
function wp_mail_set_text_body($phpmailer) {
if (empty($phpmailer->AltBody)) {$phpmailer->AltBody = strip_tags($phpmailer->Body);}
}
Then you don't need to set the headers explicitly, you can simply do:
$message ='<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
</head>
<body>
<p>Hello World! This is HTML...</p>
</body>
</html>';
wp_mail($to,$subject,$message);
Unforunately many of the functions and properties in the phpmailer class are protected, if not for that a valid alternative would be to simply check and override the MIMEHeaders property via the phpmailer_init hook before sending.
I just released a plugin to let users use html templates on WordPress and I'm playing right now on the dev version to add a simple text fallback. I did the following and in my tests I only see one boundary added and emails are arriving fine to Hotmail.
add_action( 'phpmailer_init', array($this->mailer, 'send_email' ) );
/**
* Modify php mailer body with final email
*
* @since 1.0.0
* @param object $phpmailer
*/
function send_email( $phpmailer ) {
$message = $this->add_template( apply_filters( 'mailtpl/email_content', $phpmailer->Body ) );
$phpmailer->AltBody = $this->replace_placeholders( strip_tags($phpmailer->Body) );
$phpmailer->Body = $this->replace_placeholders( $message );
}
So basically what I do in here is modify the phpmailer object , load the message inside an HTML template and set it to the Body property. Also I took the original message and set the AltBody property.