I use fetchmail to connect external pop3 and scalix smtp relay.
users sometime got 451 error, and take long time to skip that "bad" message and fetchmail always leave the "bad" message on pop3 server, then it will take more time on next fetch.
I was thinking this is a fetchmail error, but after I monitored the fetchmail with -v, I found it may be scalix smtp relay issue:
fetchmail: SMTP> MAIL FROM:<craig@craigminch.com>
fetchmail: SMTP< 250 craig@craigminch.com... Sender ok
fetchmail: SMTP> RCPT TO:<xxx.xxxxx@mydomain.com>
fetchmail: SMTP< 451 4.1.8 Domain of sender address craig@craigminch.com does not resolve
fetchmail: SMTP> RSET
fetchmail: SMTP< 250 mx01.mydomain.com Reset state
not flushed
Any one have an idea?