Here's a neat little thing:

A guy subscribed to one of our mailing lists via a web interface.

He had an automatic little vacation program set up on his account.

The message telling him that he was subscribed was sent to him.  An
autoreply was generated.

The autoreply hit listserv and a reply was created telling him that there
was no such commands was generated.

The 'no such commands' message was sent to him and an autoreply was generated.

The autoreply hit listserv and a reply was created telling him that there
was no such commands was generated.

The 'no such commands' message was sent to him and an autoreply was generated.

And so on, until his ISP got overloaded and died, thereby killing his
autoreply.

It didn't help that this started around 3 am.

The first symptom noticed at our end was that the LISTSERV postmasters
received 400-odd bounce messages from his account.  The second was that he
called us up and got kinda irate.

It took us a while to figure out what had happened, so I'm passing this
along in case any of you find yourselves in a similar situation.

-jwgh