There is no way to eliminate spam entirely, just like there is no way to eliminate junk mail that is sent to you through the Post Office. Just as the Post Office delivers all mail that is addressed to you, all email, including spam, that is addressed to you will arrive in your mailbox.
This brings up one important misconception regarding spam. People ask why they get spam that is not addressed to them. While it may appear that the spam is not addressed to you, it always is. Spammers often hide your address by putting a forged name in the To: field and putting your real address in the BCC: field, which is quite simple to do.

Unfortunately, spam will be a problem for the foreseeable future. A spammer can send hundreds of thousands of spam messages practically for free. You can imagine the amount of junk mail you would receive at your home if postage were free.

You can reduce the amount of spam that you receive in the future by following these basic tips:

Never respond to spam
Never reply to spam in any way. Don’t reply to be taken off their list, and don’t go to any links that they provide for you to supposedly unsubscribe. If you do, you are actually telling them that your email address is an active one. They will send you even more spam and probably sell your address to other spammers at a premium price. Some spam is sent strictly for that purpose—so that you will confirm your address is good by unsubscribing. Don’t do it. You will get more spam than ever. The only exception is if you know and trust the organization, and are confident that they are a reputable company that will honor your request to be removed from their list.

Never buy anything from a spam offer
Never buy anything from a spam offer. That only encourages them, as well as make you an easy mark for much more spam in the future. If no one ever bought anything from a spam offer, the problem would go away on its own. More importantly, reputable companies rarely send out unsolicited mail, so the vast majority of the spam you get is from unscrupulous individuals that aim to take advantage of you.

Avoid contests and registration
If you enter a lot of contests, or register for coupons or gifts, you may be registering for more spam. You should check the reputation of any company that you give personal information to, even if it is just your email address. Also, read their privacy policies carefully.

Look for those hidden check boxes that say you agree to receive email from their partners. They are usually pre-checked, and they are sometimes hard to find. In general, the more things you sign up for on-line, the more spam you will get over time.

Do not post your email address
If you list your email address in places such as Web based discussion groups, message boards, or Usenet Newsgroups, you will get more spam. Similarly, if your email address is listed as a point of contact on a Web page or elsewhere on the Internet, that will increase your spam. Spammers have programs that “harvest” email addresses from Web Pages, Newsgroups, and other public areas on the Internet.

Keep an unlisted email address
Consider keeping your main email address as private and “unlisted” as possible, and get a second mailbox for your public email presence. Give your private address to friends only. You would use your public address for registering with Web sites, or for posting on Newsgroups and message boards.

You can check your public account a few times a month to make sure there is nothing in there that you really need. You will be surprised at the amount of spam that starts to pile up in there, and will be thankful that it is not filling up your main mailbox. If the amount of spam to your public address gets to be too much, you can change the login name to something else.

Use disposable addresses
Consider using disposable email addresses. Several companies offer email addresses that you can use specifically for fighting spam. One benefit of a disposable address over a second public email address is that the disposable address is configured to forward to your normal email account. This way you only have to check email in one place. This is particularly helpful if there is email from that source that you do want to receive, such as a newsletter or email list.

You should use a different disposable address every time you register for something that requires your email address, or on every message board or Newsgroup on which you post. If you start getting spam delivered to one of your disposable addresses, you can easily turn off that specific address (along with any spam sent to that address). Not only that, you will be able to see from what source the spammer got your address.

Following are organizations that provide up disposable email addresses for a small fee or even free: