I have been running smartermail for years on a cheap, but low power and kind of slow VPS. However, at home I have a nicely equipped NAS that can run Smartermail in docker, and allow me to spin up a spam assassin server in docker as well. The catch is that my home ISP blocks inbound port 25. (Im not sure about outbound, as i havent tested yet). I can easily set up different subdomains like mail.domain.com, smtp.domain.com, imap.domain.com, etc. Now for the question:

Is it possible to use 2 Smartermail servers in conjunction with each other, essentially with one to interact with the outside world, and a second more powerful to do all the spam checks, and handle client connections? For reference, There are only 2 users, me and my wife, and I'm using the free version of Smartermail with all the limitations that come with using the free version. 

If this is possible, how would it be configured, and what would be the best procedure to migrate to it from the existing configuration with minimal downtime and easy data migration?