Anti-Spam Recommendations for SMTP MTAs (RFC2505)
Original Publication Date: 1999-Feb-01
Included in the Prior Art Database: 2000-Sep-13
Internet Society Requests For Comment (RFCs)
This memo gives a number of implementation recommendations for SMTP, , MTAs (Mail Transfer Agents, e.g. sendmail, ) to make them more capable of reducing the impact of spam(*).
Network Working Group G. Lindberg
Request for Comments: 2505 Chalmers University of Technology
BCP: 30 February 1999
Category: Best Current Practice
Anti-Spam Recommendations for SMTP MTAs
Status of this Memo
This document specifies an Internet Best Current Practices for the
Internet Community, and requests discussion and suggestions for
improvements. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (1999). All Rights Reserved.
This memo gives a number of implementation recommendations for SMTP,
, MTAs (Mail Transfer Agents, e.g. sendmail, ) to make them
more capable of reducing the impact of spam(*).
The intent is that these recommendations will help clean up the spam
situation, if applied on enough SMTP MTAs on the Internet, and that
they should be used as guidelines for the various MTA vendors. We are
fully aware that this is not the final solution, but if these
recommendations were included, and used, on all Internet SMTP MTAs,
things would improve considerably and give time to design a more long
term solution. The Future Work section suggests some ideas that may
be part of such a long term solution. It might, though, very well be
the case that the ultimate solution is social, political, or legal,
rather than technical in nature.
The implementor should be aware of the increased risk of denial of
service attacks that several of the proposed methods might lead to.
For example, increased number of queries to DNS servers and increased
size of logfiles might both lead to overloaded systems and system
crashes during an attack.
A brief summary of this memo is:
o Stop unauthorized mail relaying.
o Spammers then have to operate in the open; deal with them.
o Design a mail system that can handle spam.
This memo is a Best Current Practice (BCP) RFC. As such it should be
used as a guideline for SMTP MTA implementors to make their products
more capable of preventing/handling spam. Despite this being its
primary goal, an intended side effect is to suggest to the
sysadmin/Postmaster community which "anti spam knobs" an SMTP MTA is
expected to have.
However, this memo is not generally intended as a description on how
to operate an SMTP MTA - which "knobs" to turn and how to configure
the options. If suggestions are provided, they will be clearly marked
and they should be read as such.
Mass unsolicited electronic mail, often known as spam(*), has
increased considerably during a short period of time and has become a
serious threat to the Internet email community as a whole. Something
needs to be done fairly quickly.
The problem has several components:
o It is high volume, i.e. people get a lot of such mail in their
o It is completely "blind", i.e. th...