WordPress Mail Routed via Postfix SMTP Relays
By default, the WordPress wp_mail
function will not set the actual sender for sendmail
and mail
backends. This means that the Postfix relay will set the sender to the default $domain
instead of the actual sender. Which, in turn, means that when using relay maps (sender_dependent_relayhost_maps) to map senders to correct SMTP relays none of them is matched because of the sender is not set correctly…
Fortunately, the mailer class used by WordPress, PHPMailer knows how to correctly specify the sender via the chosen backend (which in WordPress is the mail
backend). By setting the Sender
property of the mailer we’re able to have Postfix identify the sender correctly.