I note there is a suggestion to port hMailServer to Linux for use with Thunderbird.
hMailServer is an open source email server application which runs on Windows. It is an easy to use email Server application which supports POP3, IMAP, and SMTP. Many other email servers separate these email protocols into 3 separate servers but hMailServer encorporates all three protocols into one Email Server application. This is a great feature in that only one server application needs to be set up instead of three separate email servers. It makes setup easier in this respect. It currently runs on all versions of Windows from Windows 7 through Windows 11. It is a very problem free email server with an Admin Utility which also runs on Windows which uses a Windows GUI to administer the settings of hMailServer. There also is a web admin utility as well. When one searches for email servers to run on their Windows PC, hMailServer has been one of the first in the search results. It practically runs without on its default settings except for necessary additions such as Domains, Accounts, etc.
The problem is that hMailServer is no longer an actively maintained application. The developer could no longer afford the time to maintain it. There are a few enthusiasts who have made their own forks but this doesn't seem to work well for those who want a Windows based email server to run locally on their private PCs. hMailServer needs an organization like Mozilla to continue maintenance of hMailServer such as updating it to any new levels of TLS encryption, etc.
With hMailServer being an open source application, Mozilla should be able to make its own Fork of hMailServer. If Mozilla wanted to improve on hMailServer's features, it would able to do so but it would not be necessary in my opinion. I have been using hMailserver as my private email server for well over 10 years without any issues and I have been using the Beta version 5.6.9-B2607 for some time. I believe this is a testament to how well the Beta versions work.
hMailServer could stand to be updated from a 32bit email server to a 64bit email server version. The enthusiasts have made their own 64bit versions but being their own Forks they are not available on the hMailServer.
I would like to suggest that Mozilla make its own version of hMailServer even if only to clone the version currently available on the https://www.hmailserver.com website. Many people would want hMailServer to continue being available as it appears to be a well liked application which even businesses have used. Thunderbird email client is able to connect to hMailServer as a client application but most email clients are able to also connect to hMailServer as an email client application. By Mozilla making hMailServer one of its available supported applications, Mozilla would be making a well known email server application continue to be available to those of us and others who use and want to use a very good Windows based email Server. It is a very robust email server in its native application but also allows for use of scripting.
I am afraid if an organization such as Mozilla doesn't offer a version of hMailServer available to the public that hMailServer will basically eventually die due to lack of maintenance. To me I believe Mozilla would be a place that hMailServer could continue to live on and be useful for those who want a private email server to run locally on their own computers such as I am doing.