Can I use Smartermail for this weird setup?

Problem reported by Scott Brewer - 2/14/2026 at 4:17 PM

Submitted

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?

2 Replies

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Douglas Foster Replied

2/14/2026 at 8:27 PM

Your ISP almost certainly blocks outbound port 25 as well. When a residential PC starts sending messages on port 25, it usually means that the PC is infected, so better ISPs block the attempt. Reputation services like SpamHaus also blacklist subnets that represent home users on dynamic ISP addresses.

It is common to configure an inbound gateway server to filter out unwanted mail before it reaches the main mail server, and an outbound gateway to perform safety checks on outbound mail. But these configurations still communicate over SMTP on port 25, so this idea cannot fix your problem.

The solution is to upgrade your home service to a business account with a static IP. It will cost more, but it will solve your problem. In urban areas, you may have a choice between Cable, Fiber, and cellular from three or more providers. So you can negotiate. The cheapest solution may be 5G cellular for the "business" email server, while keeping your existing residential service for streaming and everything else. Good luck.

Scott Brewer Replied

2/15/2026 at 11:57 PM

Well, thats what i was afraid of. My IP, while technically dynamic, hasnt changed in 8 years, so I've been trying to find a way around the port 25 issue without some 3rd party service. Thanks for the help.

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