Yes, I was kinda aware of that. However all of the bounces have started flooding into the list's notification (!) mailbox* in addition to being registered with the SES topic. I've been searching far and wide why that email address, that's only setup to capture new subscribes and unsubscribes for that list, also started pulling bounces. A little annoying.
* Just the be clear, this is different from the "reply-to" address. That mailbox really only captures genuine replies and adressee's auto-responders, which is fine.
As a test, I have now removed the reply-to address from the server settings altogether.
Can you check your amazon account and make sure that for that email address you still have the sns topics in place and that the notifications are set to go to the sns topics and not to an email address?