"Spam: unsolicited email, usually of a commercial nature."

Spam is the electronic version of junk mail, and has been around since the Internet was created. Spam filters are a way of filtering your email to remove unwanted mail based on a variety of criteria. You can block any sort of email, not just mail of a commercial nature. Blocked mail is deleted automatically - it does not even bounce back to the sender. These filters are quite flexible - some examples are provided after the instruction on how to add a spam filter below. All filters are cumulative.