Set display_errors to On and error_reporting to E_ALL.

I set error reporting and display errors on to max and still the same thing.

I don't receive any error messages.

set_error_reporting(E_ALL);
ini_set("display_errors", 1);

Yes, that's what I did as per my previous comment.

No errors at all, email gets sent, and I get a "An error occurred" message.

Please try using this CVS snapshot:

  http://snaps.php.net/php4-STABLE-latest.tar.gz
 
For Windows:
 
  http://snaps.php.net/win32/php4-win32-STABLE-latest.zip

Cannot reproduce.

Still the same thing.

Here's the code:

<?php
error_reporting(E_ALL);
ini_set("display_errors", 1);
if (!mail('email@address.com','test','test','From: email@address.com'))
echo "An error occurred";
else
echo "no error occurred";
?>

The mail gets delivered and I still get "An error occurred" as the output with nothing else.

I'm thinking it may be something to do with the way I'm configuring/compiling.

Here's my configure line:
./configure --with-openssl --enable-calendar --with-curl --with-gd --with-jpeg-dir --with-png-dir --with-zlib-dir --with-xpm-dir --with-ttf --with-freetype-dir --with-t1lib --enable-gd-native-ttf --with-gettext --with-gmp --with-iconv --with-mcal --with-mcrypt --with-mhash --with-mime-magic --with-mysql --with-mysql-lib --with-ncurses --enable-pcntl --with-jpeg-dir --with-png-dir --with-zlib-dir --with-tiff-dir --with-pspell --with-mm --enable-sysvsem --enable-sysvmsg --enable-sysvshm --with-xmlrpc --with-iconv-dir --enable-xslt --with-xslt-sablot --with-iconv-dir --with-pear --enable-zend-multibyte --enable-sockets --enable-pcntl --enable-sigchild --enable-libgcc --enable-trans-sid --enable-ftp --with-config-file-path=/usr/local/lib --prefix=/usr/local/php --with-config-file-path=/usr/local/php --disable-cli --enable-force-cgi-redirect --enable-cgi --enable-mbstring

We are still unable to reproduce it.

Some more info...

This is what I have under mail in my php.ini

[mail function]
SMTP                    =       localhost                       ;for win32 only
sendmail_from   =       me@localhost.com        ;for win32 only
sendmail_path =  /var/qmail/bin/qmail-inject


Also, I'm running netqmail 1.05 with a bunch of patches (spam, virus checking, etc).

Please provide an account @ this machine.

No feedback was provided for this bug for over a week, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".

This looks like a duplicate of bug #38342

Do you need --enable-sigchild for a particular reason?