I have witnessed somewhat normal network situations (being connected to XMPP server while connecting / disconnecting to a VPN server) that have caused a stable

I have witnessed somewhat normal network situations (being connected to XMPP server while connecting / disconnecting to a VPN server) that have caused a stable and mature Jabber client (psi) not actually send messages even though it seems that it did successfully send them. For a mature messaging protocol, that smells really really bad for any serious use.