Earlier quoted context omitted.
> Notice the "i", different from abcde@mydomain.com The username on the domain doesn't matter, only the domain itself.
> The username on the domain doesn't matter, only the domain itself. Of course it matters if it means that it wasn't actually sent from the domain in the first place and there were no "hacks" involved. You said "emails sent from your domain..." but you do know the "From" address in standard email is utterly meaningless from a security perspective right? You can just sendmail -f any.address@example.com any.target@exam…
But if you don’t check the email headers, emails are easy to spoof, hell, I did it when I was a kid...