Everyone needs to take certain concrete steps to combat the rising tide of unsolicited email, and it is not as simple as hitting the “unsubscribe” button. Here are some ways to reduce the amount of spam you receive.
1. Have multiple email addresses
Set up at least two email addresses. Use one of them only for close contacts such as friends, family and colleagues or for office work. This email should never be revealed to anyone unless specifically asked for by someone you personally know. Under no circumstances should this email be used when registering for anything on any website. This email will be your primary email address.
All other email accounts you have can be used for other less important items like registering on any website for free services and whatnot. That way any spam you get will be channeled away from your important items.
2. Do not click on the "unsubscribe” button in junk emails.
Unless it is a mailing list you subscribed to, or a store you trust, you should not use the email’s unsubscribe feature. This will confirm the spammer’s suspicions that your email is an active one and the amount of spam you receive will only increase exponentially. Simply delete all spam emails as and when they come.
3. Filters.
A good solution is to filter email through the Mail Transfer Agent or Mail User Agent (the client email program, for example, Eudora, Outlook Express). The three information sources which can be used to filter email are:
Header Filtering
The first type of filtering, which is the header filtering, is done by scanning and comparing the header and envelope of a message against a list of filters. If the address in the “From”, “X-Sender” or “Sender” fields match any in the filter list, the email is deleted.
This is the most effective method of stopping spam from plaguing your network. It makes perfect sense to filter your emails through the MTA as it is more powerful and can do it for a larger number of email accounts due to its central position.
Mailer Type Filtering
The second type of filter involves blocking emails sent out by email clients popular with spammers, such as Floodgate, Extractor, Fusion, Masse-mail, Quick Shot, NetMailer, WorldMerg, Aristotle Mail, Emailer Platinum, Master Mailer, and Calypso.
It is done by using the information stored in the “X-Mailer” field and removes an entire caste of client software. However, as with most types of Header filtering, there is a very high chance of blocking out valid emails which are sent using these senders.
IP Addresses Filtering
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The easiest way yet to filter email is by blocking out all the emails coming from IP addresses associated with sending out large amounts of spam. Again, however, you may block out legitimate mail.
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This method is a double-edged sword as it also acts as a deterrent against spamming servers. Companies who want to continue having customers will try as hard as possible to stop their servers from being spam machines in order that they do not get blocked by email clients and servers alike.
4. Do not spam, flood or hack spammers.
It is probably very tempting to retaliate against spammers by using their own techniques against them. However, this is bad idea as, usually, the site indicated as the source of the spam is not the spammer’s real site. Thus, it will be a criminal act to attack that site and you yourself will be committing the act of spamming, an ironic turn of events.
Reference
You’ve Got Spam: How to "Can" Unwanted Email
http://www.ftc.gov/bcp/conline/pubs/online/inbox.htm
How to prevent spam e-mail from reaching you?
http://www.microsoft.com/athome/security/email/fightspam.mspx