Mail Abuse Prevention System

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The Mail Abuse Prevention System (MAPS) is an organization that provides anti-spam support by maintaining a DNSBL. They provide five black lists, categorising why an address or an IP block is listed:

  • Real-time Blackhole List (RBL), the one for which MAPS is probably best known.
  • Dialup Users List (DUL), blocks of addresses that include many SOHO users.
  • Relay Spam Stopper (RSS), spam relays, e.g. hijacked servers.
  • Open Proxy Servers (OPS), naively open SMTP servers.
  • Non-confirming Mailing List (NML), marketers who use opt-out strategy.

The acronym MAPS is spam spelled backwards.


MAPS was founded in 1996 as a non-profit organization to pioneer innovative anti-spam techniques (e-mail).

The early history of MAPS is the History of DNSBLs itself. Dave Rand and Paul Vixie, well known Internet software engineers, started keeping a list of IP addresses that had sent them spam or engaged in other behavior that they found objectionable. The list became known as the Real-time Blackhole List (RBL). Many network managers wanted to use the RBL to block unwanted e-mail. Thus, Rand and Vixie created a DNS-based distribution scheme that quickly became popular.[1]

Sure that there was an absolute right to publish an anti-spam blacklist, MAPS published a "How to Sue Us" page, inviting spammers to sue them and help them create case law. In 2000 MAPS was the named defendant in no fewer than three lawsuits, being sued by Yesmail, Media3, and survey giant Harris Interactive. As the first lawsuits came in, MAPS brought in Anne P. Mitchell as their Director of Legal and Public Affairs.

In 2001 the company started to require a subscription for accessing their lists. Non-subscribed users received a dummy unlisted response. MAPS explained that their expectation to get enough funds from free support failed, forcing them to make that decision. However, the spirit of the company remained that of a non-profit organization. Their subscription page was quite hidden in their .org web site, and their fax-based subscription mechanism was rather awkward.

In 2004 MAPS became a division of Kelkea, Inc. They moved from Redwood City to San Jose, and from .org to .com. Dave Rand was the founder and CEO of Kelkea at the time.

In June 2005, Trend Micro, Inc. acquired Kelkea. That brought substantial improvement to the subscription mechanism, including a fully automated method for getting temporary subscriptions. In addition, subscribers are provided with personalised web pages where they can view reports and also set up whitelisting and blacklisting options. Whitelisting is particularly convenient, as it allows to whitelist thousands of IP addresses with a few clicks.


Proposing so many lists can confuse a MAPS subscriber; postmasters may hurriedly subscribe to all lists. The difference between an open proxy that relays spam and a, somehow open, spam relay is not clear, and so postmasters may just conclude that the more lists they use the more spam they block. However, one of MAPS lists, the DUL, is significantly different from the others. It is supposed to list addresses that are dynamically assigned to end-users (but in practice it also includes statically-allocated ones), that are not directly related to spam and there is no evidence in MAPS archives that any such address has ever been used to relay spam.

DUL's purpose was to educate users to relay mail through an acknowledged ISP, rather than running their own mail servers. That behavior would bring various advantages and disadvantages. Acknowledged ISPs can, in general, afford to monitor their systems more thoroughly in order to avoid viruses, hijackers and similar threats. Furthermore, it paves the way for effectively exploiting policies like SPF that rely upon end-user SMTP authentication in order to block email address abuse, but it prevents users of their own domain to publish a proper SPF policy. In addition, ISP email relays are incompatible with fine-grained IP address blocking: if they relay spam and get blocked, it affects all their users.

MAPS fails to disambiguate the concepts of acknowledged ISP versus end-users of IP addresses with a formal definition. While it may be relatively straightforward to recognize ISPs who are network providers, mailbox providers are easily confused with end-users of different kinds. When coupled with the ability to easily whitelist IPs by Local Internet Registry/region to correct obvious shortcomings, using the DUL to block mail may result in an obscure policy that jeopardizes the global reliability of email delivery.

What constitutes spam sources is determined by an ambiguous set of guidelines and personal opinions. MAPS have interfered with the mail services of companies simply because of considering them to be a potential spam risk, even if delivery of spam directly from each of the involved IP addresses had never occurred.[2]

It generates an amount of false positives much higher than MAPS claims to be aware of, blocking many legitimate websites and end users, and yet catching only an estimated 2% of spam.[3]

See also[edit]


  1. ^ RFC 5782
  2. ^ jamie (2000-12-13). "MAPS RBL Is Now Censorware". Slashdot. Retrieved 2011-06-17. 
  3. ^ Gwendolyn Mariano (2000-06-15). "Study finds filters catch only a fraction of spam". CNET News. Retrieved 2010-03-23. 

External links[edit]