Earlier quoted context omitted.
You don't have to switch to gmail, you can pretty reliably switch to a myriad of service providers. You could even solely switch your SMTP server to something hosted and retain message storage on your end if you wanted. It has become very difficult / unwise to host your own SMTP server, though, but that's been true for ages now. Gmail's marketshare is going to make that veeeery obvious, but it really has been a bad i…
Difficult to host smtp?! That's absolutely not true and has never been true. It's difficult to configure and set up in the first place but after that it's just updating. Source: personal experience for decades.
But it's not just postfix or sendmail you need to configure correctly and then put apt-get update/upgrade -y in cron to avoid the damage caused by making a mistake or falling asleep at the wheel. Casual self-hosters have other vectors of attack to mitigate, for example making sure sasl or whatever they may be using for imaps auth is solid, that passwords are strong and routinely changed, that php is also tight and so on. The stakes are relatively high, the efforts to compromise systems for this and other purposes are voluminous and incessant. So I'd say "it takes a village" to do this safely enough, not individual enthusiasts who cannot commit to administering a server diligently.