WP Needs to Set "Sender" and "Reply-To" or DKIM/DMARC will not work using wp-mail (via PHPMailer)

[kellogg9]

I notice that for DKIM to function (while using DMARC) correctly for outgoing mail the PHPMailer object needs to make sure the Sender and Reply-To fields match the "From" field otherwise the "Return-Path" header uses the server it is sending from causing a mismatch. When this happens DKIM fails authentication on the receiver side because it is not added to outgoing mail.

I tried adding the reply-to and sender header manually to wp_mail() but it did not work. One had to do the following:

Right now i have to manually modify the /wp-includes/pluggable.php file in the wp_mail() function to include:

if (strlen($phpmailer->Sender)==0)
{

$phpmailer->Sender = $phpmailer->From;
$phpmailer->AddReplyTo($phpmailer->From);

}

This resolves the problem and DKIM works again.