Remote Mail Checking Protocol (RFC1339)
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2000-Sep-12
Internet Society Requests For Comment (RFCs)
S. Dorner: AUTHOR [+2]
This RFC defines a protocol to provide a mail checking service to be used between a client and server pair. Typically, a small program on a client workstation would use the protocol to query a server in order to find out whether new mail has arrived for a specified user.
Network Working Group S. Dorner
Request for Comments: 1339 P. Resnick
U. of Illinois at Urbana-Champaign
Remote Mail Checking Protocol
Status of this Memo
This memo defines an Experimental Protocol for the Internet
community. Discussion and suggestions for improvement are requested.
Please refer to the current edition of the "IAB Official Protocol
Standards" for the standardization state and status of this protocol.
Distribution of this memo is unlimited.
This RFC defines a protocol to provide a mail checking service to be
used between a client and server pair. Typically, a small program on
a client workstation would use the protocol to query a server in
order to find out whether new mail has arrived for a specified user.
This RFC defines a simple, low-overhead protocol for checking the
status of a maildrop on a host. It is primarily intended for use in
adjunct with "remote mail" servers such as those implementing the
Post Office Protocol (RFC 1225). Remote mail clients must poll their
servers to discover the arrival of mail. Using one of the remote mail
protocols for periodic checking can be quite impractical and
expensive for the server since either a constant connection between
client and server must be maintained or repeated and expensive user
validations must be done. Furthermore, users on less capable
computers may not wish to devote the memory required to have a full
implementation of the client polling for mail. Thus, we feel that an
easy to implement and inexpensive to use polling scheme would be of
benefit both to mail servers and their clients.
To avoid connection overhead, the Remote Mail Checking Protocol is
based on the User Datagram Protocol (UDP), using UDP port 50 decimal
(62 octal) for the server. The protocol provides for both non-
authenticated and authenticated polling. Non-authenticated polling is
simplest for both client and server. Authenticated polling provides a
small increment of privacy, at the cost of more complexity in both
client and server (but still far less than polling with one of the
remote mail protocols).
In the non-authenticated version of the protocol, the server will
listen on port 50 for maildrop check requests for users with
maildrops on the machine. A client will send a single UDP datagram
from a randomly chosen unreserved UDP port to UDP port 50 on the
server. The datagram will contain a 32-bit (four-octet) number which
is set to all zeros (0), followed by a case-sensitive ASCII string of
a username on the server system. The server will find the maildrop on
the system for that user and determine the amount of time that has
passed since the last message in the maildrop was ...