SOLVED SMTP Restrictions Disabled but Still Blocked

[pixelaté]

Hi, I've disabled SMTP restrictions so an account can send email via a third-party SMTP server (Office 365). The issue is, for end-user accounts, port 587 is still blocked despite disabling SMTP restrictions. For root however, it's not blocked - as if SMTP restrictions were still enabled.

I've rebooted the server just to be sure to no effect. Any ideas?

Thanks,

Ian

 

[cPanelMichael]

Hello Ian,

Do you happen to use the CSF firewall application? If so, check the CSF configuration to make sure it's not blocking the connection attempt:

CSF > Firewall Configuration > SMTP Settings > SMTP_BLOCK

Block outgoing SMTP except for root, exim and mailman (forces scripts/users
to use the exim/sendmail binary instead of sockets access). This replaces the
protection as WHM > Tweak Settings > SMTP Tweaks

This option uses the iptables ipt_owner/xt_owner module and must be loaded
for it to work. It may not be available on some VPS platforms

Note: Run /etc/csf/csftest.pl to check whether this option will function on
this server

Thank you.

 

[pixelaté]

Do you happen to use the CSF firewall application?

Thanks for the response Michael That was my first thought. I checked that and the port isn't being blocked and the fact that root can access that port is another indicator.

 

[pixelaté]

Hi @cPanelMichael you were right. I wasn't aware that CSF had their own version of SMTP Restrictions. I had only looked in the open and closed ports in CSF.

For anyone else who has a similar problem, it the section of CSF Configuration titled SMTP Settings and the setting is SMTP_BLOCK. In my case, I added the user to SMTP_ALLOWUSER

Thanks for your help!

Ian

 

[cPanelMichael]

Hello @pixelaté,

I'm happy to see that helped. Thank you for updating us with the outcome.

 

[mambovince]

hi @pixelaté
I think there is some confusion about this 'feature' especially as many customers are encouraged to use external email services like Office 365 or Google Apps.

Based on your experience, would you mind giving your 'best practice' suggestions in such scenarios please?
Thank you kindly
- Vince

 

[cPanelMichael]

Hello Vince,

To solve the issue, the individual cPanel username was added to the SMTP_ALLOWUSER option under the SMTP Settings section in WHM >> CSF >> Firewall Configuration. Keep in mind that CSF is a third-party application, so it's not something that's configured or setup by default as part of a standard cPanel & WHM installation.

Thank you.