Why do I need PreciseMail Anti-Spam Gateway, if I use a blacklist to eliminate spam?
PMDF and many other mail servers support the use of third party blacklists, such as RBL (Real Time Blackhole List) which is part of the Mail Abuse Prevention System (MAPS) (http://mail-abuse.org/rbl/). These blacklists are commonly used to block spam because they verify the DNS address of a sender using a reverse DNS lookup. If the DNS address cannot be verified, the e-mail is presumed to be spam and will not be delivered. There are three problems with using blacklists to eliminate spam: • Spammers are clever and they can easily circumvent blacklists if they are not used in conjuncture with other spam- fighting techniques. Spammers can circumvent reverse DNS lookup by using forged e-mail addresses from non-existent domains or the domains of legitimate senders. • Reverse DNS that is not properly configured may result in the rejection of some valid messages. For instance, this could include mail from legitimate sites that simply have not yet registered their domain name, or during period
