@Wolf480pl@niu.moe @jerry @Aaron@boringpeople.org there is some hope in the p2p world.
BitTorrent is not exactly a "messaging" protocol, but got immensely popular.
FireChat, a p2p messaging app, got very popular during protests in Romania. Sadly it's proprietary, so I'd stay far away from it.
Briar doesn't need any introduction in this group, methinks, but is not popular at all... yet.
But, messaging and e-mail are two different things. It's not just about sending the message. It's about the infra around it.
Server run by the main developers of the project 
It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!