SOLVED Problem sending mail between cPanel servers

[hmibarrylsalter]

I'm experiencing this same issue. I have two VMs running cp 108.0.11 . AND I have whitelisted both servers with all my IPs. However, this is what I experience: I can setup a new email address on server1, send to an email on the other server2 and nothing happens, no email no warnings. Sometime later, maybe hours, one email will show up. Once one shows up to that address, anything from the one to the other from that point forward works. try a different email on server1 to server2, so thing, no error, no warnings, nothing until one of those messages sent might show up then it works. from server2 to server1, same thing, new address, problem, if enough are sent, might get one and then it works.

above the other person mentioned editing the route at the NIC, but I have no idea, is that in command prompt or inside the control panel now we are talking years ago? And when they say route is this the broadcast, I'm not smart with networking.

Please cpanel tech... Help!

 

[cPRex]

Hey there! The most likely explanation is that you're seeing the Greylisting feature happening:

Greylisting | cPanel & WHM Documentation

This interface allows you to configure Greylisting, a service that protects your server against unwanted email or spam.

docs.cpanel.net

This temporarily rejects email until the server retries later, and then the message is accepted on the second delivery attempt.

You would be able to see this in the Exim logs (/var/log/exim_mainlog) if that is what was happening. Can you check the log and confirm?

 

[hmibarrylsalter]

Actually, it was me being stupid... The domain that I kept sending to, the dns was pointed to a server that no longer existed, it somehow was not pointing to the correct server. I kept creating emails on the other server and using the same badly configured domain... It was me!

THANK YOU! because I near missed it. and if it had not been the dns, then what you explained makes sense. Why it eventually would work, no idea but it works now.

 

[cPRex]

I'm glad you were able to track that down!