They could have sent the notification letter to the old address if he stayed elsewhere fromthe current address when he overstayed the last time (assuming he went back home inbetween) and the letter would have been automatically generasted to the previous place by the DHS database, which is a slight glitch in the system.

Kind of irrelevant, he would have been deported anyway, and put in a detainer awaiting return to the last POE from where he came to whichever city he flew into from and would have been treated the same way in all likelyhood.