Email spoofing may occur in different forms, but all have a similar result: a user receives email that appears to have originated from one source when it actually was sent from another source. Email spoofing is often an attempt to trick the user into making a damaging statement or releasing sensitive information (such as passwords). (Carnegie Mellon University)

You might receive an email that asks for detailed information on a secret company project which appears to come from your boss, but instead comes from your company's competitor. Many well-known companies are daily victims of email spoofing, either accidently with a virus, or deliberately. (DAWN Ontario)

A lot of modern worms use email spoofing when they send themselves from an infected computer. This spoofing tactic has led to a great deal of finger pointing and confusion among Internet users. (Brett M.Christensen)