@darius fediverse/activitypub is currently being bridged to #xmpp/jabber (which is focused on the use-case you describe), including 'real' DM's, not just the kind transmitted and stored in open text as in mastodon. These efforts are very close to being ready for the public. My hunch is that Movim.eu might be the best first-use server for users to watch for a future gateway. BTW I would not recommend using mastodon for personal messages. #libervia