DNSBL - Criticisms

Criticisms

Email users who find their messages blocked from mail servers that use DNSBLs may object, sometimes to the extent of attacking the existence of the lists themselves. The following listing practices are controversial:

• Lists of dynamic or dial-up IP addresses. These lists most often also include "static" ADSL addresses, thus "end-user IP addresses" might have been a better description. Some mail sites choose not to accept messages from such addresses, since they are often home computers exploited by spammer viruses.
  This can seriously inconvenience SOHO users who wish to run their own mail servers on residential ISP connections or local MTAs on laptops for example. Forcing users to relay their outbound email through their ISP's mail server often yields unsatisfactory results. For example, many ISP-provided mail servers reject "foreign" "From" email addresses, i.e., those outside the ISP's domain, and this may prevent the perfectly legitimate use of personal and/or company domain names. Some ISP's outbound mail servers are chronically overloaded or unreliable (perhaps because they're swamped by spam from other users that has been forced through them). Without administrative access to the server, users have no way to determine if their mail has been successfully delivered, is still pending delivery, or has been lost and will never be delivered. Even when the ISP's outbound mail server is fast and reliable, the same problem arises when the destination mail server is overloaded or unreliable. Running one's own outbound mail server, to which one presumably has administrative access, is the only practical solution to these problems.

• Lists that include "spam-support operations", such as MAPS RBL. A spam-support operation is a site that may not directly send spam, but provides commercial services for spammers, such as hosting of Web sites that are advertised in spam. Refusal to accept mail from spam-support operations is intended as a boycott to encourage such sites to cease doing business with spammers, at the expense of inconveniencing non-spammers who use the same site as spammers.
• Predictive ("early warning") lists, notably SPEWS. SPEWS listed addresses belonging to spam-support operations, under the hypothesis that such addresses were more likely to send spam in the future. SPEWS "escalated" listings, increasing the size of the netblock listed, as a site continued to support spam.
• Some lists have unclear listing criteria and delisting may not happen automatically nor quickly. A few DNSBL operators will request payment (e.g. uceprotect.net) or donation (e.g. SORBS). Some of the many listing/delisting policies can be found in the Comparison of DNS blacklists article.
• Because lists have varying methods for adding IP addresses and/or URIs, it can be difficult for senders to configure their systems appropriately to avoid becoming listed on a DNSBL. For example, the UCEProtect DNSBL seems to list IP addresses merely once they have validated a recipient address or established a TCP connection, even if no spam message is ever delivered.

Although many have voiced objections to specific DNSBLs, few people object to the principle that mail-receiving sites should be able to reject undesired mail systematically. One who does is John Gilmore, who deliberately operates an open mail relay. Gilmore accuses DNSBL operators of violating antitrust law.

For Joe Blow to refuse emails is legal (though it's bad policy, akin to "shooting the messenger"). But if Joe and ten million friends all gang up to make a blacklist, they are exercising illegal monopoly power.

A number of parties, such as the Electronic Frontier Foundation and Peacefire, have raised concerns about some use of DNSBLs by ISPs. One joint statement issued by a group including EFF and Peacefire addressed "stealth blocking", in which ISPs use DNSBLs or other spam-blocking techniques without informing their clients.

Spammers have pursued lawsuits against DNSBL operators on similar grounds:

• In 2003, a newly formed corporation calling itself "EmarketersAmerica" filed suit against a number of DNSBL operators in Florida court. Backed by spammer Eddy Marin, the company claimed to be a trade organization of "email marketers" and that DNSBL operators Spamhaus and SPEWS were engaged in restraint of trade. The suit was eventually dismissed for lack of standing.
• In 2006, a US court ordered Spamhaus to pay $11,715,000 in damages to the spammer "e360 Insight LLC". The order was a default judgment, as Spamhaus (which is a UK operation, outside the court's jurisdiction) did not defend itself. See e360 Lawsuit. This decision was later overturned by an appeals court.