Zend\Mail ignores copy recipients (BCC or CC)

When trying to send a message with Zend\Mail to multiple BCC or CC recipients, only the first recipient in the list will receive the email. Multiple normal recipients aren't a problem.

$mail = new Mail\Message();
$mail->setBcc([
    'bcc_recipient_one@example.com',
    'bcc_recipient_two@example.com',
    'bcc_recipient_three@example.com',
]);

It doesn't make a difference to use setBcc or addBcc of the Message object.

The Issue

The problem belongs to a wrong format of the Zend\Mail header generation. It uses line-breaks between all CC or BCC recipients. As fully described in this post, the workaround is to fix the folding.

For example, this snippet:

$mail = new Mail\Message();
$mail->setFrom('test@stackoverflow.com', 'Stackoverflow Tester');
$mail->addTo('email@stackoverflow.com', 'Stackoverflow  Recipient');
$mail->setSubject('Stackoverflow Test');
$mail->setBcc(['bcc_one@so.com', 'bcc_two@so.com', 'bcc_three@so.com']);

Will create such header:

Date: Wed, 18 Jan 2018 19:11:36 +0100
From: Stackoverflow Tester <test@stackoverflow.com>
To: email@stackoverflow.com
Subject: Stackoverflow Test
Bcc: bcc_one@so.com,
 bcc_two@so.com,
 bcc_three@so.com

The problem, for at least some servers (like Micrsoft Exchange), is the line-breaks after the recipients. To fix this issue, the best way IMO would be an own Header class, because the line-breaks are hard-coded in Zend\Mail.

The Solution

Just copy \Zend\Mail\Header\Bcc class to your module and overwrite the getFieldValue function in there. With this approach you will be stay compatible on updates in the future.

public function getFieldValue($format = HeaderInterface::FORMAT_RAW)
{
    $value = parent::getFieldValue($format);
    return str_replace(Headers::FOLDING, ' ', $value);
}

The recipients will now be passed by the new header class to the Message object.

$bcc = new \MyModule\Header\Bcc();
$bcc->getAddressList()->addMany(['bcc_one@so.com', 'bcc_two@so.com', 'bcc_three@so.com']);
$mail->getHeaders()->addHeader($bcc);

That's it, the new header will be generated correctly:

Date: Wed, 18 Jan 2018 19:11:36 +0100
From: Stackoverflow Tester <test@stackoverflow.com>
To: email@stackoverflow.com
Subject: Stackoverflow Test
Bcc: bcc_one@so.com, bcc_two@so.com, bcc_three@so.com

For more details about the issue and the solution, take a look to the original post.