In a 2.2 installation of Moodle the sender address in the face-to-face settings (facetoface_fromaddress)only shows up as the name of the sender for all notification messages, but when you look at the actually email it is coming from a no reply. Therefore when a user tries to reply to a notification the 'To' address is the 'no reply' address in the messages settings for their entire Moodle installation.