Resolved postfix with SSL

[DieterWerner]

I would like to have secure postfix via SSL and need some hints.

 

[Monty]

* Go to Tools & Settings => SSL/TLS certificates
* Make sure you have a valid Let's Encrypt certificate
* Make sure that certificate is selected at "Certificate for securing mail"

That's all you need to do. Postfix will then be configured to use your server's Let's Encrypt certificate

 

[DieterWerner]

Thats the Problem:
server certificate is a self-signed and I need to secure the emails of all domains with there own certificates.

 

[Monty]

This is not (yet) possible. In order for this to work you would need to have Postfix 3.4 with SNI support, which was only released a couple of weeks ago. And as postfix is provided by the OS, you will have to wait until your OS supports Postfix 3.4 _and_ Plesk added SNI support to Postfix. Both of this will probably not happen in 2019.

So for you the only way to get rid of any SSL/TLS warnings for your mail users is:
1) Install a valid certificate for your server (preferrably Let's Encrypt)
2) Secure Plesk + mail services with that certificate
3) Tell all your customers to use your server's FQDN to retrieve and send their mail (the hostname for which you issued your certificate)

Please also read this thread:
Input - Add multidomain-support to Let´s Encrypt Certificate used for the mailserver
How to assign separate SSL certificates for different domains on a local mail server in Plesk?