I run a small server with a few dozen users, the only problem I've had is verizon.net bounces all messages claiming spam from my IP, and steadfastly refuses to whitelist me despite numerous attempts. Always just a form-letter response, despite having checked all the boxes (SPF, DKIM, rDNS). Luckily I'm happy to live without being able to email people on @verizon.net.

I'm just not willing to store all my personal and business communication with a 3rd party. It goes against the entire purpose of the standard, and I figure the day it becomes impossible to run my own server is the day I no longer use email.