A few more pieces of information would be helpful:

1. Does the script ever error out with the "COuldn't send $!" message?

Not to my knowledge. All the time I spent testing and debugging (yes, by hand. . . I should probably write something to stress-test it via automatic submissions.)

2.Does the script exit gracefully, or at all?

I don't have any error messages from the script. The one I posted comes from sendmail.

3.What are the contents of $newbody, and how large is it?

Just text, and the script handles 3 responders, each with text messages ~4K.

4.Relevant to #3, have you tried minimizing a test case where you can send any message at all, by hardcoding all the values?

back during coding/testing ( a few months ago now ) yes.

i should probably, as noted in my response to #1, bang up quick stress-tester and fire ~50 messages at it. see if i can force it to choke. . .

i really wondered if anyone else has heard of this particular error, so i'd have an extra clue or two . . .