Actually, not at all.

For instance  I was reviewing items in my Junk Mailbox and came across one allegedly from our insurance company, USAA.  Looked VERY real, correct color scheme and font it appeared - BUT just didn't smell right.  So I clicked on the From line at the top and it showed the actual 'person' it was from:

Then I looked at the email and the fake-ness was confirmed == As you probably know ## don't end in X's -plus the name there is not the one USAA has for me.