I'm seeing a very low percentage of misdelivered emails from my sendmail host. My sendmail server will try to email an address like "firstname.lastname@example.org" and the email will actually be delivered to "email@example.com" (which is my domain, the sendmail application is running on that webserver and is the email originator/sender domain.)
I've noticed this only happens for small and "weird" domains, which makes me guess that somehow the mail is undeliverable to the small domain because it's mail service is down, but just a total guess.
Has anyone seen this happen before? How can I diagnose and fix the problem?