Sudden "unroutable mail domain" errors

[GoWilkes]

In an attempt to control spam, a few days ago I enabled the Tweak setting "Prevent the user 'nobody' from sending out mail to remote addresses..." After doing so, 2 of my 52 users reported a LOT of bounced emails, most of them stating "unroutable mail domain," followed by the domain of the email recipient.

Apparently, they can send SOME emails, since they can email me (on the same server), but I do not know if the problem is sporadic, or isolated to anyone not on the same server.

It's worth noting that both users use something like Microsoft Exchange. None of my other users have reported a problem.

Assuming that the Tweak setting was the problem, I disabled it, but this had no impact. Since then, I have cleaned the Mail Queue (which only had 150 in it over 3 days; very low) and restarted Exim, but this also had no impact. Both users are still receiving the same errors.

I read in the Exim FAQ that either the DNS servers are out of step with each other or the DNS library is out of date, but that is Greek to me. How do I go about checking to see if either is true, and/or correcting the problem if it is?

TIA,

Jason

[Manuel_accu]

if you are referring to prevent user nobody from sending mails via script, then it is good idea to do so.

For that you may need phpsuexec or if your clients are sending mail via script then they need to add SMTP authentication to resolve this issue.

[AndyReed]

most of them stating "unroutable mail domain," followed by the domain of the email recipient.

Make sure that you do not have the following checked/selected?
- WHM > Tweak Settings > Prevent the user 'nobody' from sending out mail to remote addresses
- Track the origin of messages sent though the mail server by adding the X-Sender headers (exim 4.34+ required)

You also need to de-activate and delete /etc/eximmailtrap
Then run the following commands:
/scripts/eximup --force
/scripts/updateuserdomains