Unable to send mail from cpanel, possibly remote side greylist isn't handled correctly

[dandadude]

Hi!

Weird problem arised few days ago (client reported just about now).

- cPanel e-mail user sends mail to [email protected] and everything seems fine, but the [email protected] never receives the mail.
- The cPanel log contains this problem:
"SMTP error from remote mail server after end of data: 451 Temporary local problem, please try again!"
- Few minutes later I see these in the log:
"removed by root"
"Completed"

This is how it looks together:
2021-05-17 16:08:16 1liduq-004Qft-2L == [email protected] R=dkim_lookuphost T=dkim_remote_smtp defer (-46) H=mail.domain.xyz [IP.OF.MAIL.SERVER]: SMTP error from remote mail server after end of data: 451 Temporary local problem, please try again!
2021-05-17 16:10:02 1liduq-004Qft-2L removed by root
2021-05-17 16:10:02 1liduq-004Qft-2L Completed


Now from other self-installed mail servers the problem is the same, but they send the mail again successfully after few minutes, only cPanel removes the message without sending again. I would say that it is a problem on the remote side, but from other servers, all is fine...

How can this be? What should I do?

Thanks in advance!

Daniel

 

[cPRex]

Hey there! Since the error isn't coming from your side, I'm not sure there is much you can do to resolve this. If you see the outbound connection to that mailserver working properly in the logs and your message being accepted, you can be sure the error is from the remote system.

 

[dandadude]

Hi cPRex!

Thanks for your reply!

My problem is that it seems that this is a simple greylisting solution on the remote side that everykind of server can handle the right way (even other exims different from cPanel), only this cPanel server doesn't try to send the mail again, it just deletes it and I don't know why...

So this should be surely a problem on my side, but it would be a simple "resend the mail few minutes later" issue, which doesn't happen unfortunately.

My temporary solution is to use a smarthost for that domain, because that works flawlessly.

This is a problem which arised just now, before it worked perfectly...

Any new thoughts perhaps based on the above?

Thanks,
Daniel

 

[cPRex]

It might be best to create a ticket with our team so we can check the system directly.