Trying to set up email on two separate WHM servers, one is blocking SMTP connection.

[manfredmanley]

I have had server A hosting www.domain-A.com for some time now with no issues with sending or receiving email. I recently set up a server B, hosting www.domain-B.com.

Email incoming/outgoing works fine on server A.
On server B, I can receive emails fine. Sending to yahoo, hotmail, and some others works fine. However, server B cannot send to server A.

For instance, using an email set up on server B, "[email protected]" sending to "[email protected]" on server A, the message sits in the queue. Manually trying to push it out from server B gives me this error log:

LOG: MAIN
cwd=/usr/local/cpanel/whostmgr/docroot 4 args: /usr/sbin/exim -v -M 1aJ4uP-00076K-3W
delivering 1aJ4uP-00076K-3W
Connecting to mail.domain-A.com [x.x.x.91]:25 ... failed: Connection timed out (timeout=5m)
LOG: MAIN
H=mail.domain-A.com [x.x.x.91] Connection timed out
LOG: MAIN
== [email protected] R=dkim_lookuphost T=dkim_remote_smtp defer (110): Connection timed out

I can successfully telnet from my local machine to mail.domain-A.com port 25, but telnet from server-B fails.

I can telnet 25 to smtp.live.com from server-B. I don't believe it is a firewall issue.

Is there something set up on server-A that I'm overlooking that would deny server-B from connecting over SMTP? Both are running WHM/cPanel and I have root access to both servers.

 

[cPanelMichael]

Is there something set up on server-A that I'm overlooking that would deny server-B from connecting over SMTP? Both are running WHM/cPanel and I have root access to both servers.

Hello

Have you tried temporarily disabling your firewall on both servers to rule that out as the cause of the problem?

Thank you.

 

[manfredmanley]

I stopped iptables on both servers, and disabled cPhulk, if that makes any difference. I don't have any third party firewall that I know of.

Sent another test email from [email protected] to [email protected]. The message still just sits in the queue. After waiting 5 minutes, I tried manually sending from the queue and got the same error message as above.

 

[manfredmanley]

Something I noticed, if I go into the queue manager and select the message and click "deliver selected", I get the (110): Connection timed out error above. However, clicking "Deliver all" gives me a different repsonse:

LOG: MAIN
  cwd=/usr/local/cpanel/whostmgr/docroot 3 args: /usr/sbin/exim -q -v
LOG: queue_run MAIN
  Start queue run: pid=31751
delivering 1aJ6Ei-0007g2-N5 (queue run pid 31751)
LOG: retry_defer MAIN
  == [EMAIL][email protected][/EMAIL] R=dkim_lookuphost T=dkim_remote_smtp defer (-53): retry time not reached for any host
LOG: queue_run MAIN
  End queue run: pid=31751

 

[manfredmanley]

I wanted to add something else I've noticed.

The problem doesn't seem to be exclusively with server-A, because most of the emails sent from server-B seems to just hang in the mail queue. I can however send to hotmail, or yahoo from server-B.

I can SSH into server-B, but from there, if I try to telnet to server-A on port 25 it times out. If I telnet to server-A on port 587, I can connect.

From my local machine, I can telnet to server-A on both ports 25 and 587.

I also cannot ping server-A from server-B. Actually, I can't ping anything.

DNS seems to be resolving correctly, so I counted that out.

I've disabled iptables and cphulk while trying all of the above, but nothing seems to go through.

 

[cPanelMichael]

However, clicking "Deliver all" gives me a different repsonse:

That's simply informing you the initial delivery failed, but a retry attempt will occur because the message as not been in the queue long enough to stop attempting to send the message.

I suggest contacting your providers to have them determine if they are using any traffic filtering rules at all on the network side of things.

Thank you.