Troubleshooting send errors to specific host

[Drgonzodog]

I wonder if anyone could help me please?

My server is failing to send emails to accounts hosted by Mochahost. Outbound mail to all other destinations is working fine. Exim connects to the remote mailserver without issue, then waits for a period, then times out, Exinext shows:
Transport: mail.xxxxxxx.com [198.38.82.12/NULL] error 110: Connection timed out
first failed: 19-Jul-2022 11:15:31
last tried: 19-Jul-2022 17:17:24
next try at: 19-Jul-2022 19:32:24

The sending account on my server has valid SPF and DKIM records as checked via the cPanel interface and also mxtoolbox.com.

Mochahost say the problem lies with me, and they could be right, though it seems odd that they're the only host I've suddenly started having problems with.

Their response was:

Dear Client,

The issue is on the sender's side. It's not leaving the queue, meaning it's not reaching our server to be bounced back, rejected, or received.

Sincerely,

Mochahost Support Team

My question is, how do I troubleshoot this further? exim_mainlog does not show any more detail.

Any help would be gratefully received!

 

[cPRex]

Hey there! I'd start with a basic telnet test, just to confirm you can indeed reach their mailserver over port 25. From your server's command line, that would look like this:

telnet x.x.x.x 25

where x.x.x.x is the name or IP address of the remote mail server you are sending to.

If that works, which hopefully it does, you could try manually sending a message with telnet. It's best to do a web search for details on that, as there are many good guides on how to perform that work, but that would be a good test to see if the mail connection works in general and there is an issue specific to Exim.

In general, though, your logic makes sense that if every other mailserver is fine, including larger ones like Gmail, it would seem unlikely to be an issue on your server.

 

[Drgonzodog]

Hi,

Thanks for your response. I will try as you suggest.

 

[cPRex]

Let me know what you find!

 

[Drgonzodog]

Hi,

Sending a mail via telnet worked:

telnet 198.38.xx.xx 25
Trying 198.38.xx.xx...
Connected to 198.38.xx.xx
Escape character is '^]'.
220-mocha3020.mochahost.com ESMTP Exim 4.95 #2 Wed, 20 Jul 2022 04:40:25 -0500
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.
ehlo my.server.com
250-mocha3020.mochahost.com Hello my.server.com [xx.xx.xx.xx]
250-SIZE 52428800
250-8BITMIME
250-PIPELINING
250-PIPE_CONNECT
250-AUTH PLAIN LOGIN
250-STARTTLS
250 HELP
mail from: [email protected]
250 OK
Rcpt to: [email protected]
data
250 Accepted
354 Enter message, ending with "." on a line by itself
subject: Test
From: [email protected]
To: [email protected]
Test
.
250 OK id=1oE6Dc-00GkHu-UA
quit
221 mocha3020.mochahost.com closing connection
Connection closed by foreign host.

.. so I guess it's something to do with my Exim configuration that this specific host doesn't like?

 

[cPRex]

That's very strange. You're always welcome to submit a ticket to our support team so we can check things directly on the machine.

You could also run this command:

tail -f /var/log/exim_mainlog

while sending an email from your server to the recipient experiencing the issue to see if there is any additional feedback in the logs about this behavior, as that will update the log on the screen in real-time while the message is sent.

 

[Drgonzodog]

Thanks for that, I'll create a ticket. I've tried watching the exim log in real time via CSF while sending to the problem server, but nothing shed any more light on the issue.

 

[cPRex]

Once you have that ticket number please post it here so I can follow along.

 

[Drgonzodog]

Thanks cPRex, the ticket id is: #94467311

 

[cPRex]

Thanks for that - I'm following along with that ticket on my end now.

 

[cPRex]

It looks like we were able to confirm the remote host is blocking your IP once we had access to the server.