TPC.int was kind of crazy. They had a stunt DNS server that made it more convenient to use, so you could mail an address like remote-printer@441234567890.tpc.int (referring to a nonexistent number in Bedford in the usual bigendian E.164 order) and it would be automatically converted to official little-endian RFC 1528 format remote-printer@0.9.8.7.6.5.4.3.2.1.4.4.tpc.int, after which the usual DNS delegation mechanisms could model the E.164 delegations to route the fax to the nearest server.