Sendmail issue (not generating ndrs)
My problem is that i am not receiving ndrs when a message is undeliverable. For example, when the email address is invalid.
This is the way my mail flows:
Client >> Exchage 2003 server >> Redhat Sendmail Server >> Internet
Internet >> Redhat Sendmail >> spam filter >> exchange
My sendmail server just acts as a relay. We have the mailertable setup to foward any mail for our domain. we are using spam cop to filter through some of the mail before its forwarded internally. And other than that were not doing anything fancy.
When I send a message to an invalid external address I see an error in the maillog stating user unknown. Yet I never receive an undeliverable message. So I started to troubleshoot this by sending to an invalid address then searching the maillogs for my email address to see if an ndr was sent back. I found no trace of any messages going back to my address. So then I went to my yahoo account and sent an email to the same invalid address and immediatly recieved an ndr.
This system has been online for some time now so I don't know if someone purposely configured it to not send ndrs. Please let me know if you have any ideas on where I should begin to investigate this issue.