Maybe. You'll frequently find many stores/communities/services saying "hotmail/yahoo/___ users, we haven't been getting your emails" because those services aren't quite as big as Gmail and are getting spam-holed or whatever. I'm sure spam filtering already gives a major hit to free email services. If a mail server started up that explicitly permits in its ToS propagation of hate speech and terrorist threats, it's probably going to get blocklisted by all major email services, no?