What does Boxing Day have to do with boxing?
/nas'tee-gram/ 1. A network packet or e-mail message (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 e-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.