RFC 1339 (rfc1339) - Page 2 of 6
Remote Mail Checking Protocol
Alternative Format: Original Text Document
RFC 1339 Remote Mail Checking Protocol June 1992
remote mail protocols).
Non-Authenticated Protocol
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 appended, as well
as the amount of time that has passed since the maildrop was last
accessed for reading. The server will then send back a single UDP
datagram containing three 32-bit numbers in network byte order to the
originating port on the client. Again, the first will be zero (0),
the second will contain the number of seconds plus one since the last
addition to the specified user's maildrop and the third will contain
the number of seconds plus one since the last read on the user's
maildrop. If the username provided does not exist, if the maildrop is
not on the system or if the maildrop is empty, the server will send
back zero (0) in the last two numbers for its reply. The client will
consider the maildrop to contain new mail if the number of seconds
since the last read access is greater than or equal to the number of
seconds since the last addition access of the maildrop and either
number is non-zero, old mail if the number of seconds since the last
read access is less than or equal to the number of seconds since the
last addition access of the maildrop and either number is non-zero,
and empty if both numbers are zero.
Authenticated Protocol
The authenticated protocol operates identically to the non-
authenticated protocol with the exception of the first interaction
between the server and the client. After the client has sent its
initial request containing the requested username, the server will
send back a single UDP packet containing three 32-bit numbers. The
first number will be a bit-mask instead of the normal 32-bits of
zero. The bit-mask will indicate a request for authentication. Each
bit in the mask represents a type of authentication that the server
accepts. The bits (with the least significant bit numbered 0, and the
most significant bit 31) are defined as follows:
Dorner & Resnick