Disclosure of recipient’s forward email address when my email bounces

Question

A few times I had a situation like this:

1. I sent an email to foobar@example.com.

2. For this email, I received a delivery failure report, giving reasons like "550 5.1.1" (user unknown) or "552-5.7.0" (security issue).

3. In this delivery failure report, a different email address is mentioned

   Mail delivery to the following recipient has finally failed:

   john.doe@example.edu

   or

   Final-Recipient: rfc822; john.doe@example.edu
   Original-Recipient: rfc822;john.doe@example.edu

So, I assume that the owner of foobar@example.com decided to forward emails to john.doe@example.edu. But I only learned about this email address thanks to an error. This could be a privacy problem for the recipient.

Is it standards-compliant to disclose the forward email address in this context? If yes, is there a way to prevent such a disclosure?

Answer 1

Is there a way to prevent disclose the forward email address?

Linux/Unix:
Instead of direct forwarding in ~/.forward (or via aliases) forward using e.g. procmail.

~/.forward does not change envelope sender.
procmail by default changes it to account doing forward. man procmailex provides an example how to avoid forwarding loops by setting and checking X-Loop: header.