Whoson

Whoson (WHO iS ONline) is a proposed Internet protocol that allows Internet server programs know if a particular (dynamically allocated) IP address is currently allocated to a known (trusted) user and, optionally, the identity of the said user. The protocol could be used by an SMTP Message Transfer System in conjunction with anti-spam-relaying filters to implement a scheme similar to the one described here to allow roaming customers use their "home" SMTP server to submit email while connected from a "foreign" network.