Resolved Force Plesk to use port 25 alternative (Digital Ocean refuses to open 25)

[Paul Larson]

Server operating system version

Ubuntu 22.04

Plesk version and microupdate number

18.0.59 Update #2, last updated on Mar 21, 2024 04:10 PM

There are numerous threads on this topic.

I haven't found a way to force Plesk to use port 587. In the mail server settings, when I enable port 587, upon sending tests with Roundcube, the maillog indicates port 25 is still being used.

Mar 21 18:25:41 my-server postfix/smtp[99165]: connect to alt1.gmail-smtp-in.l.google.com[209.85.202.27]:25: Connection timed out

In this case, in particular on a Digital Ocean droplet, it seems a dead end. I have a Postmark SMTP account for example - how could I enable that in Plesk *without* disabling Webmail/Roundcube?

At least in my test, installing MSMTP (relay only) for STMP disabled both RoundCube and Horde.

I suppose I could survive this if I could Roundcube or Horde to use an outgoing port besides 25.

 

[Kaspar]

Email messages are always sent from the senders (email) server to the recipient (email) server via port 25. Because that's the port all other (email) servers are listening on for receiving email. Every other email port, like 587, are for connections between either an email client (such as an App on your phone) and an email server or between an email server and a relay server (who will send the email message out to the recipient email server via port 25).

The whole reason DO (and many other providers) block port 25 is because they don't allow their servers to be used as sending servers. Having other port that would allow you to sent emails would defeat that purpose. You can however relay email to another server (or mail service) on any other port.

Edit: I missed that you are using MSMTP to actually relay email messages. Sorry about that. I recommend using Postfix instead and configure it to relay email.

This support article explains how to configure postfix to relay email to SendGrid. But the same steps can be used to relay email to any other server or mail service.

https://support.plesk.com/hc/en-us/articles/12377374645655-How-to-configure-Postfix-on-a-Plesk-server-to-send-emails-using-SendGrid

 

[Paul Larson]

"You can however relay email to another server (or mail service) on any other port."

If you're referring to Plesk's MSMTP, that's fine. But it forcibly disabled Webmail from what I can tell.

 

[Kaspar]

I misread your opening post. I edited my previous post with information on using Postfix to relay email.

 

[Paul Larson]

Excellent! That worked. And in my case, supplemented by these Postmark specifics (using 587 instead of port 25 in the example)

Can I configure Postfix to send through Postmark? | Postmark Support Center

If you use our SMTP server option, you can use a smarthost in Postfix to relay mail through Postmark. A big advantage of this is that it requires no changes…

postmarkapp.com

Thank you!