I'm tempted to do that, but how much effort does it take to have something rock solid with no downtime?
Or in general, what are the `uptime` over `time investment` and `security` over `time investment` curves like?
It took about 1 day to set it all up, where most of the time was spent waiting for DNS changes and for Microsoft to de-list my IP from their blacklist (I probably got a bad IP from DigitalOcean).
After that I have logged in to the instance every two weeks to update the machine, haven't had any problems as of yet.
The uptime shouldn't be any problem, as the other mail providers should retry sending their mail, it's even mentioned in the RFC: https://tools.ietf.org/html/rfc5321#section-4.5.4
Hopefully I haven't missed any mail when updating mailcow-dockerized, I'll never know, hehe.
Really easy and a great experience, compared to doing it from scratch.
But you're asking the wrong questions. Email itself has retries built in, it doesn't need perfect uptime. What you should be asking is how badly Gmail deciding you might be a spammer and not caring about fixing that for one person is going to torpedo your deliverability rate.
By default, they both apply strict security practices so you won't have an open relay, worried about domain masking etc.
Either are about a day to set up and its mostly DNS.