service unavailable for a few email messages

[Dave Chamberlin]

We send all oracle email (from alerts) via email relay. We send hundreds of emails every day, but there are few emails that are failing. A sample returned email (my server is saturn) says:
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
< saturn.merit.com #5.5.0 SMTP; 501 5.5.4 Invalid Address>

The mail log shows:
mailer=relay, relay=oramail.merit.com [10.2.9.107], stat=Service unavailable Apr 10 13:21:44 saturn sendmail[27312]: NAA27293: NAA27312: DSN: Service unavailable

My DNS is via the host file only. So what exactly is the culprit?

[Steven E. Protter · Accepted solution]

Shalom,

I've worked with sendmail for some time. The 5.5.4 error is from the receipient server configuration indicating the intended recipient is not valid. You may wish to bump up the loglevel in sendmail.cf in order to see if one of the scripts has a bad recipient. Otherwise check for problems on the receiving server.

The log entry shows that oramail.merit.com simply refused to accept the message. This could be due to overload, too many messages, or sendmail being down. Sendmail has throttle capabilities that may be invoked if configured.

The evidence thus far does not point to a problem with the sending server, though a general network problem could explain the log message, not the 5.5.4 error. I would look at the receiving server logs and see what it says, because thats where my sendmail experience says the problem is coming from.

SEP