PHP4 and mail() suddenly not working

I'm running Apache 1.3.12 on RH Linux 6.2 w/ PHP 4.0.0 as a DSO module and qmail. On two separate occasions in the last few weeks, mail() has stopped sending mail apparently out of the blue for all of the several dozen virtual domains using mail in PHP. No errors, no complaints, but there is no record in the maillog of any mail going out. Restarting httpd doesn't seem to fix it, but rebooting did the trick. Then, after an undetermined amount of time, it stops working again. Qmail has been running flawlessly for years (and still is). PHP3 was sending mail through these same scripts for many months, and PHP4 worked for weeks without any apparent problems. I have '/usr/sbin/sendmail -t' configured and verified via phpinfo() that it takes, and it does work for awhile. This is one of the worst kind of problems because there is no indication that anything is wrong since the program doesn't complain, the info that should be mailed is lost forever, and nobody knows it until days later when we get a call saying the client hasn't gotten any orders. Any thoughts on what might be happening? Thanks! _______________________ Ron Bickers Logic Etc, Inc. rbickers@logicetc.com