My sendmail server occasionally fails at delivering an email. I get a Service unavailable error:
Feb 7 23:45:01 ip-10-101-xx-xx sm-mta: q17Nj0RQ003836: to=<email@example.com>, ctladdr=<firstname.lastname@example.org> (33/33), delay=00:00:01, xdelay=00:00:01, mailer=esmtp, pri=121203, relay=smtp.xxxx.xxxx.edu. [144.92.xx.xx], dsn=5.0.0, stat=Service unavailable
My question is how can I tell if the service at my end was down or the service at the recipient? If it's my problem, how can I solve it?
I'm asking because I'm getting a lot of these errors lately...