MyName@missing_domain

I was looking at some emails in a folder of an active account. For organization purposes, the folder contains emails both from me and from the people I communicated with.

Several of the emails that I sent say they are from:

MyName@missing_domain

It says this in the From column of the list, and when I open the individual email.

The domain is active. The email address is active. Also, I ran a db repair; that didn’t help.

Any ideas ?