A homelab enthusiast (a hobbyist who runs server gear at home) has shut down a Microsoft Exchange server that had been running since 1999. Its last job now belongs to Postfix, an open-source mail transfer agent, on Ubuntu Server LTS.
The user, posting as Meta4X on r/homelab on November 5, started with Exchange 5.5 on Windows NT 4. The install then moved through Exchange 2000, 2003, 2007, 2010, 2013, 2016 and 2019. Meta4X said access to Microsoft's software through MSDN, TechNet and the Microsoft Action Pack made that upgrade chain possible. Mailboxes and mail delivery had already moved to Microsoft 365. Exchange survived only as a relay for alerts from hardware and software on the home network.
The obvious reading is that Microsoft's licensing pushed the server out. Exchange 2019 has reached end of support, and the on-premises product is now Exchange Server Subscription Edition, which carries ongoing licensing requirements. But a commenter pointed out that existing Exchange 2019 licenses can be used with the new edition under qualifying arrangements. Meta4X said they had not known that, and that they probably would have put off the shutdown if they had. So this was a choice, not an eviction.
That makes it a familiar kind of story: a heavyweight system kept alive by one small chore. Relaying alerts is a job Postfix handles with far less machinery. Meta4X also plans to add STARTTLS (which upgrades a plain SMTP connection to an encrypted one), Let's Encrypt certificates and boot encryption. Those are intentions; the post does not show them deployed.
The thread offered other exits. Some commenters had moved to Mailcow, one suggested Grommunio for people who want to keep mail on-premises, and others were content to leave hosting to cloud providers.
Postfix does not settle the security question on its own. Its documentation says enabling TLS can encrypt SMTP sessions, but administrators still have to handle certificates and decide what happens when a remote server does not support encryption.