"Mail Notify" is a protocol used by the WebTV/MSN TV service that dispatches real-time notifications to online clients to check for new mail. The only mention of this protocol's existence so far outside of this wiki is in an internal Microsoft document . "Mail Notify" runs on top of UDP, and alongside sending connected boxes notifications for mail, supposedly tracked how many were online as well.
Mail Notify is a simple broadcast protocol that would send periodic datagrams to online clients to make them check for mail. As soon as a client connected to the WebTV/MSN TV service, it would be expected to open a UDP socket on port 6666 to be able to receive packets from the Mail Notify server. The contents of the datagrams are unknown, but the official WebTV/MSN TV clients do not verify them and only check if a packet has been sent from Mail Notify at all. Clients would respond to the datagrams sent from Mail Notify by making a
GET request to
wtv-notices:/notices on the WTVP servers, likely to get info on new mail.