Silently bouncing messages mean messages can get lost. For example, when I
fetch manually, I can see this:
fetchmail: SMTP error: 550 maximum allowed line length is 998 octets, got 1006
fetchmail: mail from MAILER-DAEMON@ bounced to
fetchmail: SMTP listener refused delivery
If fetchmail is running as daemon like it usually is, I get no indication that
I missed a message. At the very least, in failures like this, fetchmail should
send its error messages through as an email, including the subject and sender,
so that the user knows they missed a message and can investigate.