What do you mean by Postage Stamp?
A Postage Stamp in this context is a verifiable proof
that the sender spent computer time for computing the proof. It is computed using strong cryptographic∞
techniques which prevent forgery .
One stamps is computed for each recipient of the email (so if the email is being sent to three people, it will contain three stamps). These stamps require computer time or to compute, i.e. it is guaranteed to take a certain minimum amount of time to compute a stamp depending on the StampValue
This computed proof is added to the email header when the email is sent. The receiver can verify the stamp quickly to make sure it is genuine and has not been tampered with.
An example of a MBound
stamp is given below: