Email can be received but not send

[Timile]

Hi,

I'm trying to fix a problem who recently appear (4 days) and is reaching all accounts on my WHM server.

All accounts can receive email but cannot send. Problem is simple but cannot find a solution.

Classic configuration WHM with Exim as mail server.

What I've tried:
- reboot email server, use email troubleshooting, email Email Deliverability tool. All tool are looking good, they are all saying all is good.
- Checking my firewall config, testing connection with mail server : Gmail on port 25 : ok, Yahoo on port 25 : ok, icloud on port 25 : ok.
- Try to force delivering an email but connection always timeout after 5m.

Here's my log when I try to send email:
LOG: MAIN
cwd=/usr/local/cpanel/whostmgr/docroot 4 args: /usr/sbin/exim -v -M 1mQCXG-0001Mv-Og
delivering 1mQCXG-0001Mv-Og
LOG: MAIN
Sender identification U=leam D=**********.com [email protected]******.com
Connecting to mx02.mail.icloud.com [17.57.154.7]:25 ... failed: Connection timed out (timeout=5m)
LOG: MAIN
H=mx02.mail.icloud.com [17.57.154.7] Connection timed out

Can someone have idea how I can repair this? Thank you.

 

[cPJustinD]

Hey there! Can you run these commands via SSH and provide me the output?

curl portquiz.net:25
traceroute -p 25 smtp.gmail.com

This should verify that outbound connections over port 25 are working as expected. Please be sure to remove any sensitive information such as IP address from the output.

 

[Timile]

Hi!

I've run the commands and here's the output:

curl portquiz.net:25
220-hostname.hostname.com ESMTP Exim 4.94.2 #2 Tue, 14 Sep 2021 15:08:27 -0400
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.
500 unrecognized command
500 unrecognized command
500 unrecognized command
500 Too many unrecognized commands

And:
traceroute to smtp.gmail.com (209.85.144.109), 30 hops max, 60 byte packets
1 * * *
2 * * *
3 * * *
4 * * *
5 * * * 6 * * * 7 * * * 8 * * * 9 * * *10 * * *11 * * *12 * * *13 * * *14 * * *15 * * *16 * * *17 * * *18 * * *19 * * *20 * * *21 * * *22 * * *23 * * *24 * * *25 * * *26 * * *27 * * *28 * * *29 * * *30 * * *

Waiting for your answer, thank you!

 

[cPJustinD]

Hello again. It appears there is some outbound restriction over port 25 occurring. Can you try disabling SMTP restrictions to see if that allows you to connect via port 25 successfully?

How to disable SMTP Restrictions

 

[Timile]

Hi,

I've disabled SMTP restrictions, reboot and still cannot send email. I've retry to run the two commands and here the new results:

curl portquiz.net:25
curl: (7) Failed connect to portquiz.net:25; Connection timed out

And:

traceroute -p 25 smtp.gmail.com
traceroute to smtp.gmail.com (173.194.68.108), 30 hops max, 60 byte packets
1 * * *
2 * * *
3 * * *
4 * * *
5 * * *
6 *00 * *
7 * * *
8 * * * 9 * * *10 * * *11 * * *12 * * *13 * * *14 * * *15 * * *16 * * *17 * * *18 * * *19 * * *20 * * *21 * * *22 * * *23 * * *24 * * *25 * * *26 * * *27 * * *28 * * *29 * * *30 * * *

 

[cPJustinD]

Thank you for that output. As the SMTP restrictions are disabled, and the outbound connections are still timing out, it appears the restriction is coming from a local or network firewall.

You will need to work with your server administrator or hosting provider for further assistance in determining why the port is restricted and taking the appropriate measures to ensure that it is open for outbound requests. We've also published an article that covers this topic here:

Why can I receive, but not send, emails?

 

[M_Z]

@Timile,

Were you able to solve this, how did you solve it?

We are facing the same problem.

Would be great if you could help out.

 

[cPRex]

@M_Z - the most likely explanation is that your hosting provider has blocked outbound traffic on port 25 to reduce spam.