I’ve been running my own mail server for about 15 years now… Let me offer some insights.

• Its used by me and the family, so I do have other users who expect things to work.
• I used commodity hardware, with a Linux host (and guest).
• the mail server runs in a VM, so it is trivial to: stop, copying the VM to USB, restart.
• Maintaining uptime isn’t too bad, but when the mail server goes down, you need to get onto it quickly. I’ve had power supplies fail, HDD’s fail, memory fail.
• If you should happen to be out of town when a failure occurs (I’ve had this twice), then the server stays dead until you are back. That does not make your users happy. If its more than 4 days, then the SMTP standard says email is lost.
• There have also been a few software issues with Zimbra (my current tool) - the stats daemon filled the disk, the upgrader broke permissions all over the place multiple times. Each of these requires time to investigate, research online etc. Snapshotting is awesome! Right now I have a problem where the VM disk file is growing, but the space used inside the VM is not. I have zero’d out free space and compacted the VM but don’t know why it is happening yet. More research needed.
• You will learn to hate blocklists. There are many, and there are meta blocklists. You have to watch them because at any time, you will be added and your email will silently get dropped. Sometimes the blocklist trashes whole subnets because of a single actor, sometimes even more, and so you will get included due to other bad actors. Getting off a blocklist is hard… you send emails, you fill in web forms, you look for a contact details, you wait… Then some number of days/weeks later, you are off again.
• You have to learn DKIM, SPF, DMARK, managing DNS etc.
• I used to use self-signed certs and live with the warnings. Now I used Lets Encrypt, which is awesome!.
• You can try to get reverse DNS working, but that’s up to your ISP (who usually don’t care, so good luck). No rDNS can be viewed as bad by email recipients so your spam score starts at >0.
• If you run it at home, you will be part of a block of IPs that are known to be home users, so your spam score starts at >0.
• I’m lucky in that I run it on a spare public IP address on my server housed at work. But that will need to change soon.

I started using native Linux mailboxes, later added roundcube (web UI), investigated Mailinabox, but now use zimbra. That gives me calendar/contact sharing, email/calendar/contacts to iOS devices (which is the main way my family get email), and lots more. Moving data from one to the other took a couple of days of effort. (Yeah… I know its supposed to be trivial, but its not when you include tool research, testing, execution one at a time etc).

Bottom line - you will learn lots, you will lose many weekends and sometimes a weekday here or there as you try to handle emergencies, it will never be set-and-forget.

My original rational was learning, privacy and my own domain and nicer looking email addresses than john1234@gmail.com. I’m looking for an online alternative as its time to lighten the load, but I have a lot of services that we use in Zimbra.

Good luck with it!