I've configured the SMTP Publisher to receive emails, but when I send them to FME Server I get undelivered responses.
I looked at the email.log for the FME Server Publishers and I see:
"WARN Email received for unknown recipient temail address], so dropped
What does this mean?
It looks like FME Server is receiving the email, but doesn't know what to do with it.
If you've set up an email publication (SMTP) on FME Server to receive emails to and you try sending an email to there's a chance FME Server will still get that email, but because it hasn't been configured to receive emails at that address it will drop them (what you're seeing in the email.log file), and you will get an undelivered response.
The best thing to do would be to double check your email smtp publications that they are configured correctly.
I had a user with a similar issue but the publication existed. They found that deleting and then adding the publication again fixed the issue. I'm not sure why this is but it's worth a try.