The e-mail was provided to CNN on the condition that the sender's name be redacted.

CNN: Brown: E-mail shows Bush glad FEMA took Katrina flak

Your mail-handling software would scan each message to see if either the sender's name could be found in your personal directory or a magic word could be found in the subject field.

FORBES: Side Lines

While the name tagged to an email sender might suggest "NatWest Bank", a nonsensical email address or one clearly outside the country should raise suspicion.

BBC: Q&A: Phishing for your precious data