SMTP server no effective way to validate the sender's email address. SMTP proxy SMTP proxies allow combating spam in real time, combining sender's behavior controls, providing legitimate users immediate feedback, eliminating a need for quarantine. Spamtrapping Spamtrapping is the seeding of an email address so that spammers can find it, but normal users can not. If the email address is used then the sender must be a spammer and they are black listed. As an example, if the email address "spamtrap@example.org" is placed in the source HTML of a web site in a way that it isn't displayed on the web page, human visitors to the website would not see it. Spammers, on the other hand, use web page scrapers and bots to harvest email addresses from HTML source code - so they would find this address. When the spammer later sends to the address the spamtrap knows this is highly likely to be a spammer and can take appropriate action. Statistical content filtering Statistical, or Bayesian, filtering once set up requires no administrative maintenance per se: instead, users mark messages as spam or nonspam and the filtering software learns from these judgements. Thus, it is matched to the end user's needs, and as long as users consistently mark/tag the emails, can respond quickly to changes in spam content. Statistical filters typically also look at message headers, considering not just the content but also peculiarities of the transport mechanism of the email. Software programs that implement statistical filtering include Bogofilter, DSPAM, SpamBayes, ASSP, CRM114, the email programs Mozilla and Mozilla Thunderbird, Mailwasher, and later revisions of SpamAssassin. Tarpits A tarpit is any server software which intentionally responds extremely slowly to client commands. By running a tarpit which treats acceptable mail normally and known spam slowly or which appears to be an open mail relay, a site can slow down the rate at which spammers can inject messages into the mail facility. Depending on the server and internet speed, a tarpit can slow an attack by a factor of around 500. Many systems will simply disconnect if the server doesn't respond quickly, which will eliminate the spam. However, a few legitimate email systems will also not deal correctly with these delays. The fundamental idea is to slow the attack so that the perpetrator has to waste time without any significant success. An organization can successfully deploy a tarpit if it is