17. The method of claim 11 , wherein the method further comprises the step of: when the reputation score is better than a second predefined threshold, performing a second specified action associated with responding to messages that are not unsolicited, wherein the first predefined threshold is different from the second predefined threshold.
21. The method of claim 17 , wherein the step of performing the second specified action comprises associating the message with a second flag, wherein the second flag indicates that the message is estimated to be valid.