It doesn't seem like I can use my own domain. That's actually extremely important as I don't want to end up in the same scenario I'm in (can't just pack up and move). It seems my options are:

* Host myself and deal with possibly losing mail, high spam, rejected mail or downtime.

* Pay for a service to handle this for me (either partially like Mailgun or fully like FastMail).

If I want more uptime, I could lease a VPS. Either way, I have to pay up somewhere (money or loss of data). If I'm paying, I'd rather back a company that cares about privacy, like FastMail.