Given recent events, I don't think Amazon Prime is that necessary anymore.
Mail servers, sure. The big issue there is another annoying pseudo-monopoly issue where so many major email servers assume anything not from [major email server] is spam, so you may not even get to communicate properly. More sticks for the fire.
I'm anything but a major mail provider and I don't have any issues. I did have some hiccups around 2008 and had to implement DMARC-DKIM. I use strict delivery so my mail server must delivery all mail directly.
Occasionally people have a vanity domain email that bounces back to me. I have to search the headers for the actual email address and re-send.
2 examples are not having an amazon prime account and running my own mail server.