"The more exclamation points used in an email (or other posting), the more likely it is a complete lie. This is also true for excessive capital letters."
This law is related to author Terry Pratchett's field test for insanity, in which an increasing number of exclamation marks from one to five indicates increased separation from reality, with five exclamation marks being an infallible indicator of the speaker or writer being "someone who wears their underwear on the outside".
Other examples of The Law of Exclamation include phrases such as: "this is true, it ACTUALLY HAPPENED to me!!!!" or "This is SPOOKY!!! I thought it was just an urban legend, but it isn't!!!!".