How many are still running their own mail server?
I have been running Zimbra for years, now, with "Let's Encrypt" certificates. It works well, but periodically, the certification gets scrambled, and I have to manually fix it. The symptoms are the same each time, but the fix seems to be different each time, meaning I have not yet found a general solution, but It only happens one or twice a year.
They no longer provide a "Community" edition, so I am stranded, meaning, I would move to a supported platform, if the migration was easy, but for now it is working, and I hope it continues to work.
I can highly recommend Zimbra; Zimbra is what ComCast uses, not that ComCast is any great endorsement beyond the volume that they handle.
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