bcc-header issues with Horde_Mime_Mail

bcc-header issues with Horde_Mime_Mail

This issue caused some uncertainty since I was not sure if the headers were broken due to missing quotes. See https://github.com/conjoon/php-lib-conjoon/issues/17.

Turns out that the way I assembled an email from a full text and converting it back to an instance of Horde_Mime_Mail does not consider the type of the internal representation of the bcc-field properly. It's related to Horde_Mail_Rfc822_List::_normalize and how values passed from Horde_Mime_Mail::send() are processed by it.

Here's a code snippet that shows how I use a full text message as input, then converting it back to an instance of Horde_Mime_Mail with headers processed by Horde_Mime_Headers::parseHeaders(). The original message has a bcc header-field:

(Original code can be found here).

HordeClient.php

         $target = $item->getFullMsg(false);
         // ... 
         $headers = Horde_Mime_Headers::parseHeaders($target);

         $mail = new Horde_Mime_Mail($headers);
         $part = Horde_Mime_Part::parseMessage($target);
         $mail->setBasePart($part);

         $mailer = $this->getMailer($account);
         $mail->send($mailer);   

Horde_Mime_Mail temporarily removes the bcc header and stores it in a property named _bcc, then uses this value to add it to the recipients' addresses later on in send(). This is so the bcc-header is not appearing in the source of the message the recipients receive (see https://www.ietf.org/rfc/rfc2822.txt, Section 3.6.3 and 5):

"The "Bcc:" field (where the "Bcc" means "Blind Carbon Copy") contains addresses of recipients of the message whose addresses are not to be revealed to other recipients of the message." https://www.ietf.org/rfc/rfc2822.txt, Section 3.6.3

This is a part of Horde_mime_Mail::send():

Horde/Mime/Mail.php

        /* Build recipients. */
        $recipients = clone $this->_recipients;
        foreach (array('to', 'cc') as $header) {
            if ($h = $this->_headers[$header]) {
                $recipients->add($h->getAddressList());
            }
        }
        if ($this->_bcc) {
            $recipients->add($this->_bcc);
        }

The source above shows that for to / cc the method getAddressList() is being called, while the value of _bcc gets passed to the add() method. However, _bcc holds in this case an instance of Horde_Mime_Headers_Addresses, which Horde_Mail_Rfc822_List::_normalize() does not consider. The value is ultimately ignored, Emails are not being sent to the addresses mentioned in the bcc header.

Here's the implementation of normalize():

Horde/Mail/Rfc822/List.php

    protected function _normalize($obs)
    {
        $add = array();

        if (!($obs instanceof Horde_Mail_Rfc822_List) &&
            !is_array($obs)) {
            $obs = array($obs);
        }

        foreach ($obs as $val) {
            if (is_string($val)) {
                $rfc822 = new Horde_Mail_Rfc822();
                $val = $rfc822->parseAddressList($val);
            }

            if ($val instanceof Horde_Mail_Rfc822_List) {
                $val->setIteratorFilter(self::BASE_ELEMENTS);
                foreach ($val as $val2) {
                    $add[] = $val2;
                }
            } elseif ($val instanceof Horde_Mail_Rfc822_Object) {
                $add[] = $val;
            }
        }

        return $add;
    }

A possible fix is to call getAddressList() on _bcc in Horde_Mime_Mail::send() or check for this type in the normalize()-method of Horde_Mail_Rfc822_List:

Horde/Mail/Rfc822/List.php.diff

    protected function _normalize($obs)
    {
        $add = array();


+       if ($obs instanceof Horde_Mime_Headers_Addresses) {
+           $obs = $obs->getAddressList();
+       }
     
        if (!($obs instanceof Horde_Mail_Rfc822_List) &&
            !is_array($obs)) {
            $obs = array($obs);
        }

Fixing this in Horde/Mime/Mail.php is also possible, although I do not know if that would cause any side effect since I could not find the expected type of _bcc. It gets checked in '_normalize()' (see above) so I guess this would be the better place to apply the fix, instead of doing this:

Horde/Mime/Mail.php.diff

        /* Build recipients. */
        $recipients = clone $this->_recipients;
        foreach (array('to', 'cc') as $header) {
            if ($h = $this->_headers[$header]) {
                $recipients->add($h->getAddressList());
            }
        }
        if ($this->_bcc) {
-            $recipients->add($this->_bcc);
+            $recipients->add($this->_bcc->getAddressList()); 
        }

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Update 21.03.2023: PR available here