Email was one I figured I would get an answer for. I know plenty of people do it, but I’m not sure if I’d trust myself to do it right.

It's not even about doing it right. It's a PITA to manage when big players can just decide to block your server and then you'll be jumping trough hoops with Microsofts spam filtering program and whatnot just go get your messages trough. It's got very little to do if you've managed things right on your end, random issues with delivery just pop out of the thin air and it's your job to monitor it, swear by your mothers name to the big players that you'll play nicely and hope that their robotic overlords are satisfied with your time and effort.

And if you host email for anyone else it gets exponentially worse. I've been doing it long enough that apparently my server has a reputation now so those cases aren't as frequent as they used to, but they still pop up now and then and it takes time to figure it out with no other reward than the issue goes away, until it returns without any way to really know why.