c.im is one of the many independent Mastodon servers you can use to participate in the fediverse.
C.IM is a general, mainly English-speaking Mastodon instance.

Server stats:

3.2K
active users

Gold gab ich für Eisen

@sammi @daniel @maple

"why are we conflating email with IM?"

E.g. because both are used for communication between people.

"xmpp clients, to me anyway, don't meet my requirements of e2ee by default"

You are not enforced to use them. As is an open standard and there are clients, you are free to make one that meets your standards.