Source : Free On-Line Dictionary of Computing

nastygram
     
        /nas'tee-gram/ 1. A protocol packet or item of e-mail (the
        latter is also called a {letterbomb}) that takes advantage of
        misfeatures or security holes on the target system to do
        untoward things.
     
        2. Disapproving mail, especially from a {net.god}, pursuant to
        a violation of {netiquette} or a complaint about failure to
        correct some mail- or news-transmission problem.  Compare
        {shitogram}, {mailbomb}.
     
        3. A status report from an unhappy, and probably picky,
        customer.  "What did Corporate say in today's nastygram?"
     
        4. [deprecated] An error reply by mail from a {daemon}; in
        particular, a {bounce message}.
     
        [{Jargon File}]