Broken pipes, time outs, PHP, and mail

PHP Gurus, I have a set of scripts that sends out emails to a list of about 150 people. Sometimes it works fine. Other times, it dies part way through the list, and in my error logs I get this output: fputs() [<a href='function.fputs'>function.fputs</a>]: send of 22 bytes failed with errno=32 Broken pipe /public_html/class.smtp.php 489 The code that sends the mail is derived from here: http://www.phpclasses.org/browse/file/920.html It's mostly rock solid code, so far as I know, so I suspect the problem to more with my server settings or something. That said, I don't know what differentiates a failed mailing and a successful one. After a Google search, it seems "broken pipes" are a matter of time outs. That's about as far as I understand it, though. Can anyone throw me a tip as to how I might diagnose this problem? Thank you for any advice. -- Dave M G