install docker in the same host that PMG installed

Have not tried this myself - so cannot guarantee that it would work - but don't see any blocker to this

However - why would you want to have a Docker engine on your mail gateway? - mixing multiple services on the same host has the potential for causing service outages, which would not be necessary)?
 

About

The Proxmox community has been around for many years and offers help and support for Proxmox VE, Proxmox Backup Server, and Proxmox Mail Gateway.
We think our community is one of the best thanks to people like you!

Get your subscription!

The Proxmox team works very hard to make sure you are running the best software and getting stable updates and security enhancements, as well as quick enterprise support. Tens of thousands of happy customers have a Proxmox subscription. Get yours easily in our online shop.

Buy now!