I looked into this problem today while working on v4.7.7 and I too am unable to make the bounce work properly. My bounces go into the bit bucket somewhere.
The plugin sets up the phpMailer object correctly and I’ve played around a couple of setting within the mailer object without success. In the reading I’ve done support for this varies wildly from hosting provider to hosting provider.
I am not sure what to do with this but I cannot reliably make it work.
I did some more looking into this and I added some code to properly set the Return-Path header. After doing so and everything looking correct in debug mode, I found the following in the WordPress class-phpmailer.php file:
/**
* The Return-Path of the message.
* If empty, it will be set to either From or Sender.
* @type string
* @deprecated Email senders should never set a return-path header;
* it's the receiver's job (RFC5321 section 4.4), so this no longer does anything.
* @link https://tools.ietf.org/html/rfc5321#section-4.4 RFC5321 reference
*/
public $ReturnPath = '';
The $ReturnPath property is not used anywhere else within PhpMailer. The comments indicate it has been deprecated. I also tried adding a Reply-To header which does show up in the debug output but doesn’t seem to have the desired effect.
It looks like I cannot support a Bounce so I will likely remove this option in a future release.
