Most ISPs don&#x27;t allow inbound (or, often, outbound) connections on port 25, so the number of people who can run mail servers at home is pretty limited.  I think even Cox stopped allowing it a while ago, and they were among the most lenient of the big ISPs.  (Comcast hasn&#x27;t allowed it for a while.)<p>That, I think, is why the distribution managers don&#x27;t make the default configurations a little more friendly&#x2F;sane; most users aren&#x27;t interested in installing a MTA to do anything but local delivery or smarthosting, and the people who are, are probably going to tweak the configs to death anyway, so it&#x27;s not worth spending the time making it run well and securely straight out of the box.<p>It wouldn&#x27;t be too hard to build a &quot;mailserver in a box&quot; with (say) Debian + Postfix + LetsEncrypt + BIND that you could stand up in an hour and be reasonably secure (and I&#x27;d be kinda surprised if that doesn&#x27;t exist in some form already), but I don&#x27;t know how many people would want it who aren&#x27;t running mailservers already, and have the capability of doing so.