Reply-by-Email 曾有效,现在已损坏

Thanks @pfaffman, that fixed it. Sounds like you’ve seen this before- is there something that should have been done better? In our case, there were repercussions beyond just not receiving user emails:

VERP relies on incoming emails. So we weren’t handling bounces and complaints for a few days, our reputation with SES plummeted, and they suspended our outgoing emails.