Some companies you may have had dealings with sell their mailing lists to third parties, spammers included. Spammers also use “robots” to scour the Internet and harvest any email addresses that they find. If you post to newsgroups you are also at risk of spammers picking up your email address and sending you junk email. To get adequate spam protection and get rid of Spam, you really need more than one email address. This is an essential element of proper Spam control.
"If you did not have to subscribe to get it, there is little chance that un subscribing will get rid of Spam"