Spam email can clog your inbox even if you use a good spam filter. Junk emailers are always looking for new ways to defeat filters and get their messages in front of your eyes. Legitimate companies will remove your email address from their spam lists if you use the unsubscribe link included in their messages. It is much harder to get off a scam company's list, but you can take some steps to stop the barrage of junk email.
Determine whether the company that sent you the spam email is legitimate or questionable. You can recognize the names of legitimate companies because they will be online or bricks-and-mortar businesses you already know about. You won't recognize the names of questionable companies, and they are often selling sketchy items such as prescription drugs, get-rich-quick schemes, male enhancement products or fake designer goods.
Click the unsubscribe link at the bottom of the spam message if it was sent by a reputable company. This may take your name off the list immediately, or it may take you to a website where you must click a confirmation button.
Report the spam message to the sender's ISP and email provider if the message is from a questionable company. The Spamhaus Project says you should never click the unsubscribe link in this type of message. At best it will tell the spammer that your email address is active and that your mail is being read. At worst, you might be taken to a malware-infected website. The ISP or email provider may be able to shut down the spammer if it gets enough complaints.
Protect your email address so it will not get on any other spam lists. The McAfee anti-virus company advises users not to post email address on the Internet or to include it on forms for companies with privacy policies that allow them to sell it or share it. Make a special email address just for sign-ups and limit the people to whom you give your work and personal addresses.
According to The Spamhaus Project you can sign up with a service called Spam Cop to reduce junk mail and to automate reporting of spam to the senders' ISPs and email providers.
The Spamhaus Project warns against signing up for email address removal services. Some charge a fee and do not perform any service, while others are free but are a front to collect addresses. You will get even more junk email if you sign up.