I'm looking for a decentralized instant message system (e.g. XMPP, SIP, ...) where I can be sure that I receive all messages, even if I'm not connected when the message is sent [ Obviously, I'll only receive them when I'm back online. ]
IIUC there is some XMPP features that allow such reliable delivery, but it seems that it's not widely supported by clients. What Debian clients, using which protocols, can provide reliable instant messaging? Stefan PS: Bonus points if that feature is also available on an Android application that's Free Software.