I remember in the mid-late 90's how poorly the Exchange server ran that there was a nix server for inbound email just to throttle the ingress. When it was upgraded to a 4-socket server, there was concern when the *nix guys just let everything that was being held during the upgrade through, and it just chugged along. But the moment of panic was palpable. The Unix guys really didn't like that business internals and apps were running from Windows services, so thought it would be funny to try to knock over the new mail server.

Today, you can run mailcow/mailu with all the options on a relatively modest vps. I'm on a cable provider that locks down residential customers and charges over 2x as much for business, so it's cheaper to use VPSes.

On RPi, I've mostly opted to use SSD + USB Adapters as they've been significantly more reliable that SD. There's lots of cases that make this configuration a breeze. That said, I've mostly been running Mini PCs since COVID when the RPi got to be more expensive all-in and slower.

They make high endurance microSD cards that can handle a lot more writes before failing.

OTOH, I corrupted a card by turning off the Pi in middle of writing.

Interesting, what tools did you use for email hosting?

I’m scared of self hosting a mailbox.

>The point of failure for all of these machines has been the SD card. They seem to last 4 years almost to the day. I suppose if I set up a RAMdisk they might last longer, but honestly, for the price of an SD card it’s not really worth my time.

There are "Industrial" SD cards which should last considerably longer, you can look up a few people have done their own testing. They can be slower but that shouldn't be a blocker for an email server on a pi.