SMTP Service Extension for Remote Message Queue Starting (RFC1985)
Original Publication Date: 1996-Aug-01
Included in the Prior Art Database: 2000-Sep-13
Internet Society Requests For Comment (RFCs)
This memo defines an extension to the SMTP service whereby an SMTP client and server may interact to give the server an opportunity to start the processing of its queues for messages to go to a given host. This extension is meant to be used in startup conditions as well as for mail nodes that have transient connections to their service providers.
Network Working Group J. De Winter
Request for Comments: 1985 Wildbear Consulting, Inc.
Category: Standards Track August 1996
SMTP Service Extension
for Remote Message Queue Starting
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
This memo defines an extension to the SMTP service whereby an SMTP
client and server may interact to give the server an opportunity to
start the processing of its queues for messages to go to a given
host. This extension is meant to be used in startup conditions as
well as for mail nodes that have transient connections to their
The TURN command was a valid attempt to address the problem of having
to start the processing for the mail queue on a remote machine.
However, the TURN command presents a large security loophole. As
there is no verification of the remote host name, the TURN command
could be used by a rogue system to download the mail for a site other
Therefore, this memo introduces the ETRN command. This command uses
the mechanism defined in  to define extensions to the SMTP service
whereby a client ("sender-SMTP") may request that the server
("receiver-SMTP") start the processing of its mail queues for
messages that are waiting at the server for the client machine. If
any messages are at the server for the client, then the server should
create a new SMTP session and send the messages at that time.
2. Framework for the ETRN Extension
The following service extension is therefore defined:
(1) the name of the SMTP service extension is "Remote Queue
(2) the EHLO keyword value associated with this extension is "ETRN",
with no associated parameters;
(3) one additional verb, ETRN, with a single parameter that
specifies the name of the client(s) to start processing for;
(4) no additional SMTP verbs are defined by this extension.
The remainder of this memo specifies how support for the extension
affects the behavior of an SMTP client and server.
3. The Remote Queue Processing Declaration service extension
To save money, many small companies want to only maintain transient