Avoid Mail Delivery System Bounce Forward

Question

I have the following mail setup:

This is what happens at the numbered stages:

1. some spam-address (which actually does not exist) sends spam to info@xyz.org
2. the info@xyz.org has an auto-reply configured which is sent automatically to spam@spam.org (which does not really exist)
3. since spam@spam.org does not really exist, the info@xyz.org receives a Mail Delivery System message from the Mailer-Daemon (the daemon is omitted from the picture for the sake of clarity). The Mail Delivery System message looks like this: https://i.stack.imgur.com/bROIo.png
4. My issue here is, that this Mail Delivery System mail gets forwarded to person1@private.com (etc...) because I have configured a mail forward from info@xyz.org to person1@private.com, etc...

What can I do to avoid step 4, that is, the auto forward from the mail delivery system error message to the forward mail addresses (person1@private.com)

One solution would be to disable the Mail Delivery System messages at the email-server. However, I think this is not really smart, because sometimes, I would like to receive these error messages, in case they are useful.

Answer 1

My recommendation is to change the envelope sender on the auto-reply sent at step (2) of your flow. It is this envelope sender address, which will receive any error messages at step (3).

You can use an empty envelope sender at step (2). That will prevent the error message being generated at step (3). In the SMTP session it would look like this:

MAIL From:<>

Alternatively you can create a separate address for using as the envelope sender at step (2). Then the error message will still be generated at step (3). The error message generated at that step will have empty envelope sender and a destination address matching the envelope sender, you used in step (2). By using a separate address for this purpose, you can treat it differently and avoid step (4).

You do not have to change the From: address inside the email headers at step (2).

Whatever you do I also strongly recommend that you ensure the mail you send at step (2) contains enough information to uniquely identify which mail at step (1) triggered it. That essentially means include the Message-ID of (1) somewhere inside the mail generated at (2).