Yeah? And where is your server hardware located? If it's on a VPS somewhere, well, how can you trust them? If it's at home, it's extra space and electricity that's being used.
At the end of the day, email IS NOT secure. If you're paying for a service and they can say they're not reading your emails and they will respect your privacy, well that's good enough for me.
At home servers are extra space and electricity, AND potential outages if your ISP isn't 100% stable. I had outages sporadically for 2 weeks because a squirrel chewed through some coax outside my house. Im glad I didn't sporadically bounce emails for 2 weeks during that time. I'm sure a major provider has redundancy and controls in place for failovers... a single server in your house probably doesn't.
Why do you think they'll respect your privacy any more than gmail? I think that's a serious misconception. They have no way to guarantee that to you, so believing it is a rather bad idea. They could be sitting back and reading the latest issue of your personal emails and you'd have no way to tell, so I don't see how it can be argued that FastMail is at all superior in that regard.
At the end of the day, email IS NOT secure. If you're paying for a service and they can say they're not reading your emails and they will respect your privacy, well that's good enough for me.