Spam filters are designed to block unwanted messages generated by unethical senders. Presently, there are different spam filter programs in the market available for email users to purchase. These programs are designed differently, which means that their methods of detecting spam vary.

Businesses which require email messaging for information dissemination would find it helpful to know the different methods used by spam filters. This will in turn help them tailor there message's content as well as their mailing procedures. Thus, being aware of spam filter programs can help in the optimization of any internet campaign.

The most common type of spam filter is the Content-Based Filter. This type of filter as the name suggests, looks on symbols, words or phrases in the subject line, headers and content of the message which are suspicious. The filtering process is very dependent to phrases and words chosen by the user as spam, this means that spam messages with words or phrases not included in the list of the user will make it to the inbox time and again unless the user creates another filter to deal with those words and phrases. The good side of this filter is, it can be fashioned in anyway the user wishes to.

Another type of spam filter is the Bayesian Filter, unlike content-based filter; Bayesian filter undergoes ‘training' where the filter learns the difference between a spam and a legitimate email. During this ‘training' messages are broken into tokens and these tokens are then stored in databases (tokens of good messages are separated from those of spam). This type of filter requires minimal maintenance and can adapt easily to users' usual message, just like if the user is a medical practitioner, anything that relates to medical field will be considered as good. The primary drawback of Bayesian filter is that optimum filtering will not take place immediately, since the filter is dependent on the messages on which it is trained.

In addition, there is a Blacklist-Whitelist filter where the whitelist is composed of the ‘good' email addresses and the blacklist is composed of email addresses believed to send spam. This kind of filter ensures that received emails are from whitelisted senders only and any address aside from the whitelisted ones will be blocked. With this, email users can expect a zero false negative. The main disadvantage of this filter is that, whenever a real-time blacklist (RBL) is used, there is a tendency that the whole IP is considered as spam sender, though only a part of it used to send spam.

Challenge-Response Filter on the other hand sends messages to unknown senders asking them to do further action/step to justify their intention of sending the email. These further actions can be a request for the senders' website to ensure that the email is legitimate. This type of filter is quite applicable to low traffic email users.

Community filter is another type of spam filter. This filter has a central server where users can send suspected spam; the server itself then saves the ‘fingerprint' of the message to the database. When enough users flagged the message as spam, the ‘fingerprints' of the message will be blocked in the future. But before a spam is blocked, many users have already opened it.

If your business makes use of email in sending promotional or newsletters, you should at least know if your email address is in the real-time blacklists so that you can apply for whitelisting. And at least know the basic symbols, words and phrases to be avoided in sending emails. Try visiting www.emailreach.com. for more information about spam filters.