Delta Chat
Delta Chat is my favorite mobile email client too - I love it and use it every day.
Email is is great but not good for every use case. Instead of email, XMPP is much better if you want to have statuses (online, is typing, …) or groups because of different authorization options.
→ system comparison
And even XMPP, the very protocol that should promote instant messaging networks, did in fact failed (it still a niche)
Provider independend chat based on XMPP is used in background very often and growing again. This is also shown by the frequency of mention in the press and in articles/comparisons. Awareness has changed and is growing steadily.
Please have a look at: