Managing your own server is in general pretty hard (for sending or receiving). Unless you want to invest a lot of time in security and so on. It's simply way overwhelming. And if you don't invest in security, you are inviting trouble.
Sure. I've been running my own mail server for almost 20 years, but you seemed to imply that the bare act of sending email from a personal server to Gmail was a bad idea for some reason.
I've been running my own email server since... forever. In 1985 it was uucp ! paths and sendmail. I got a "for real" domain just for email in 1993, still over uucp dialup. DSL always on in 1999. But it does become harder as time goes on.
On the list of computing tasks I do every day, running my email server is WAY down there on the list of difficulty. Email servers are probably even easier than web servers.
Which doesn't necessarily mean you take necessary steps to seriously protect it. Or may be it means you are an expert and all that is trivial for you. But in general it's clearly not.
