Slackware Linux has switched to the Postfix MTA as its default MTA as of an update to the development version today.
https://mirrors.slackware.com/slackware/slackware64-current/ChangeLog.txt "Default MTA" in Slackware terms means "the only MTA". Sendmail 8.15.2 has been moved out of the main distro into "extra" packages, and a new libmilter package has been created therefrom, for Postfix milter support. Postfix has been available in the Slackbuilds.org user build script repository for many years, but there were a few issues with that package for me. I believe I have addressed those issues to my satisfaction. If anyone is interested, the new build script can be found here: https://mirrors.slackware.com/slackware/slackware64-current/source/n/postfix/postfix.SlackBuild On my own Slackware-based servers for years, what I have done was start with a patched Slackbuilds.org build script (to remove the Slackware-isms of gzipped man pages and the hard-coded version strings in configuration paths), and then for future upgrades, I "make upgrade" from source. The gzipped man pages are there, but the version-named directories are referred to with symlinks. "make upgrade" from source won't be happy with the man pages, but otherwise might work (I admit, I have not yet tried it.) In any case I believe that the Slackware upgradepkg(8) process will be safe, as it will invoke "postfix upgrade-configuration" in the "doinst.sh" script. Please let me know if you have any feedback. While I am not the actual package maintainer (in Slackware there is only one over all packages), I can and will bring any issues to his attention. Offlist email per .signature below is fine, but for likely faster response, see the URL below. -- http://rob0.nodns4.us/ Offlist GMX mail is seen only if "/dev/rob0" is in the Subject: