BIG PROBLEM - Exim: could not complete sender verify

[jandafields]

Any email I send out, even to myself, immediately comes back with this error in the exim log:

could not complete sender verify

I don't know of anything that has recently changed with exim.

For temporary, I totally disabled sender verification in exim so I could at least have email working...

What does sender verification rely on? What should I look for to fix it?

Thanks.

[PlatinumServerM]

It tests to make sure the sender's address is valid. But this is a common issue and a lot of people disable that because it is too strict and winds up losing legit email.

[jandafields]

I found the problem. It uses mailman for some reason, and if you chmod 000 mailman, it breaks exim sender verification.