have a look at https://account.conversations.im I'm - the author of the essay and developer of Conversations - are running this server with one of the ejabberd developers. That server is really up-to-date and has everything you need to run Conversations. (every XEP mentioned in my essay)

If you want alternatives there is jabber.at, which has also proven to be very well maintained in the past.

And there is jabber.de (but they don't have MAM (yet))