Postfix adds an appropriate X- header (X-Postfix-Sender:), so you do not need to create one via phpmailer. RFC's call for an optional Original-recipient field, but mandatory Final-recipient field is a fair substitute.
It's all in the status code, if you can find one.
Report #1
Could not parse code - Could not parse code -
Report #2
leopold_skryd@example.com
5.0.0
Permanent Failure - A permanent failure is one which is not likely to be resolved by resending the message in the current form. Some change to the message or the destination must be made for successful delivery. Other undefined Status - Other undefined status is the only undefined error code. It should be used for all errors for which only the class of the error is known.
is not the same as the reported status code, but it seems to be more descriptive, so it should be extracted (if possible).
Report #1
couldn't decode
Report #2
leopold_skryd@example.com
550 Access from ip address 87.237.123.24 blocked. Visit http://win.example.com/cgi-bin/support_bl?ip=87.237.123.24
Permanent Failure - A permanent failure is one which is not likely to be resolved by resending the message in the current form. Some change to the message or the destination must be made for successful delivery. Other or undefined protocol status - Something was wrong with the protocol necessary to deliver the message to the next hop and the problem cannot be well expressed with any of the other provided detail codes.
Just in case we don't have an Original-recipient: field, or a X-Postfix-Sender: field, we can retrieve information from the (optional) returned message body part
From: webmaster@myphorum.de
To: leopold_skryd@example.com
Subject: Registration Confirmation
Files:
1.eml