Chapter 12. Sender Verification

In this chapter, we look at the area of sender verification. Sender verification systems are methods by which an email recipient requires the sender to perform some sort of action to prove that the message he or she is sending is legitimate. The fact that spammers usually forge their return addresses means that verification of the fake From: address will fail and the spam message will be blocked.

The areas of positive response and sender verification are very closely related, with positive response being a specific type of sender verification. The term “positive response” implies a response after the message is sent. However, sender verification can happen before or after the message is sent. For the purposes ...

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