The following practices from McAfee Security will help you reduce the thousands of unwanted messages from entering your email inbox:

• What is unsolicited commercial email (aka "spam")?
  Marketers see email as a quick and cheap way to promote their goods and services. Many companies send highly targeted email to users who have opted-in to receive these messages. Typically, these messages are of interest to the user. Examples of these include newsletters and notifications of sales and/or promotions to specific goods or services. Ensuring the privacy of the user, companies will place an “unsubscribe” mechanism that will effectively take the user off future mailing lists.
  
  Unsolicited commercial email (UCE or “spam”) is sent to users without their expressed permission. Currently, the amount of spam a user receives on a daily basis easily outnumbers the number of legitimate email. Many times, spammers will provide a fake “opt-out” button in the message that is either a “dead” link or a way to confirm with the spammer that the email address is valid for future mailings. Email spam is a proliferating Internet problem. Last year, an estimated 2.3 billion spam messages were sent on a daily basis. This number is expected to jump to an astounding 14.5 billion by the end of 2006!¹
  
  
• Why should I care about email spam?
  Inbox Pollution
  Within a business environment, critical email addresses, e.g. “sales@” or “support@” can fall victim to inbox pollution. Spammers can overload a critical email address with so much spam that the address is essentially rendered unusable.
  
  Internet Fraud
  On first glance, many unsolicited commercial offers may seem both legitimate and compelling. Unfortunately, these offers lead to deceptive Web sites, set up to capture credit card information for the purposes of online fraud. According to a study by the Federal Trade Commission (FTC), 66% of all spam email they collected contained false “From” lines, “Subject” lines, and message text.²
  
  Unsuitable Content
  Spam email can disguise itself with harmless subject lines, only to reveal pornographic material within the message body. While preventing children from viewing unsuitable content is important for parents, businesses must also address the legal liabilities associated with pornographic material being sent to an employee’s inbox
  
  
• How do email spammers get my email address?
  Every time you send your email address out into the world, you are exposing yourself and your business to the deluge of spam email. To make the problem worse, email lists are also sold and resold within spammer networks, greatly increasing the volume of spam sent to a user’s email address.
  
  Email Harvesting
  Spammers employ simple but effective tactics to harvest email addresses from the Internet. Using free spider software, spammers get access to email addresses without a user’s consent.

¹ Radicati Group 2002

²FTC press release, "FTC Measures False Claims Inherent in Random Spam" (April 2003)