Sendmail Stopped Working After Upgrade

I had a client upgrade his PHP from 4.? to 4.3.9. An important script
stopped working. It seems to work fine, but it uses the mail() function and
sendmail to send notifications. The email never arrives. The script worked
fine before the upgrade. Variables in php.ini seem to be set correctly. The
system is Redhat Linux. With the upgrade, a new php.ini file was created,
which had far more in it than it did before. Setting all of the variables
back to what they were before the upgrade didn't seem to help.

Does anyone know of a reason why 4.3.9 doesn't work right with sendmail?

Rex

What's the return value of mail()?

false/true?

Can you post the bit of code that sends the mail?
Is sendmail installed, and does sendmail work via the command line?

Thanks for the reply.

We cut down the php.ini file to just the variables we knew we needed and it
all worked.

Can't post the code due to confidentiality agreements. It's a simple mail()
that doesn't look at the return code.

Sendmail is installed and does work via the command line. Everything works
now. We just don't know what about the php.ini file was preventing it and
what portion removed enabled it to work again.

Rex