SMTPS and Submission Configuration

Configuring SMTPS and Submission

SMTPS and Submission are email protocols for encrypted authentication for outgoing email. By default, they use ports 465 and 587.

To set them up, you'd first need to add an SSL certificate for one of your Virtual Servers. Virtualmin can then copy that SSL certificate into Postfix for SMTPS and Submission.

To generate a self-signed SSL certificate, you can simply go into Edit Virtual Server for the domain in question, and set SSL Website Enabled.

Then, click Server Configuration -> Manage SSL Certificate. From there, you can click Copy to Postfix in order to enable SMTPS and Submission with your newly generated self-signed SSL certificate.

This will of course work just fine with a commercial SSL certificate. For instructions on setting up a commercial SSL certificate, see these instructions:


This is not working.. I'm using thunderbird and I can't connect smtp over ssl. Also, my emails are not encrypted when they are sent to another server.

I am having the same problem, after properly installing the SSL certificate (with Let's Encrypt) and copying them to Dovecot and Postfix, the Postfix configuration does not accept any connections... It is probably a bug. Dovecot works as far as I have seen.

linuxtavarez's picture
Submitted by linuxtavarez on Thu, 06/25/2020 - 20:29

Google has disabled STARTTL and only enables encrypted connections so I was not receiving emails from Google servers, after following this article and enabling SSL/TLS encryption for Postfix, I received all emails at once.

Linux System Administrator @ Liquid Web