To be honest, in the last 20 years or so of self-hosting emails, the most common failure points were • Gmail marked an email as spam, but still delivered it. E

To be honest, in the last 20 years or so of self-hosting emails, the most common failure points were • Gmail marked an email as spam, but still delivered it. Easily cleared up, no hard feelings on either side. • Someone else self-hosts some abysmally maintained Exchange 2003 setup that just about barely works with GMail and Office365, after the MSP irresponsible for it gets enough verbal beatings. Impossible to get to work.