PGP solves that problem, and yours. Running your own MTA comes at a price. You need a domain, certificates, your ISP needs to not block port 25, possibility of abuse (so separate IP, server, domain, certificates), server which costs money needs to be maintained and draws power and requires space, and another responsibility to maintain. Disclaimer: It is possible containers mitigate some of the above problems. It is also a legacy protocol. Just run PGP on top of it and use any free provider out there. If you don't use that you can assume Google's oversight (the NSA) sees your mail.
