Debugging sendmail - dsn=5.0.0

I am getting alot of the following messages from an ISP when sending out emails. Is there any way to get more information from these ? Users are reporting that they are not receiving any emails?

Jul 5 17:02:50 smtp sendmail[11239]: r6592of7011232: to=, delay=00:00:00, xdelay=00:00:00, mailer=esmtp, pri=168781, relay=mx12.example.com.com. [123.123.123.132], dsn=5.0.0, stat=Service unavailable

Is it possible to start running debug mode for sendmail?

Diden

Solution 1:

Sendmail: Sending outgoing test message in verbose/debug mode

As root you may send a test message in verbose mode.
You should get full transcript of SMTP session to the remote SMTP server.

(echo: subject: test; echo) | /usr/sbin/sendmail -v -Am -i [email protected]

You may add additional debug/tracking command line options:
-d8.20 - tracking DNS queuries
-d60.5 - tracking maps (databases) queries