|Have you ever wondered what would happen if you replied to spam and asked them to remove you from their list? If they aren't a reputable company (which many aren't) you will be flagged as a "live prospect" and your name will probably be sold to other spammers. By replying, you let them know that there is a real person at an active e-mail account. You may not be able to e-mail them back for a number of reasons. The Valid Sender Analyzer looks for these reasons and increases the spam points if the e-mail fails the tests. If the "From" address is not the same as the "Reply To" address, it may indicate deception and some points will be added. The addresses not matching often occurs when a company hires a spam company. The "Reply To" goes back to the spam company so they can handle the backlash. The Valid Sender Analyzer also looks for an empty "From" address. If there isn't anybody to whom you can send a reply, it isn't likely that the e-mail is good. The final steps are to verify that there is an IP address to which a reply could be sent. If that works, then a quick test lets the Valid Sender Analyzer know whether there is a real computer receiving e-mail on the other end.