Suppose that my email address forwards incoming emails to an archiving service.
That is, firstname.lastname@example.org forwards to tom@ArchivingService.com
Now suppose that example.com is hosted at OpalStack, and that ArchivingService decides (roguishly) to blacklist OpalStack.
Then people who send email to email@example.com will receive (after an oddly long delay of a few days) an "Undelivered Mail Returned to Sender" notification from MAILER-DAEMON@de.opalstack.com saying that their message to "Original-Recipient: firstname.lastname@example.org" could not be delivered to "Final-Recipient: tom@ArchivingService.com" because "address is black listed".
Should this be happening?
For all I know, it is the expected and correct behaviour.
But I find it startling. It reveals a surprising amount of information to my correspondents.
For example, the fact that ArchivingService is blacklisting OpalStack ... is it appropriate for my correspondents to learn this?
Most of them won't know what OpalStack is, and will be unsettled to find that the mere act of writing to me has tipped them into a shadowy realm where organizations with unknown names are blacklisting each other.
It also reveals my forwarding routes to my correspondents. Is that appropriate?
What if I were to forward my all emails to an organization called I_am_only_pretending_to_work_and_am_actually_on_a_beach.com ?