I have this test script:
<?

$res=Mail("martin@douda.net","test","just a test");
printf("%d",$res);

?>

If I run this script in standalone php, it sends a mail to me as expected, but if I run this via apache module mod_php,
the function mail() fails (returns 0). Even when error_reporting is set to 15, it does not report any error.
Both standalone and moduled phps are using same configuration file. I have tested 
sendmail_path="/usr/sbin/sendmail -t" and not setting sendmail_path at all, both showing same behavior.
And of course, I've restarted apache each time I've changed php configuration.

I have tried replacing sendmail binary with my test script, 
which have shown that sendmail is not run at all for some reason.



My php configuration:
;; EXTENSION LOADING
extension_dir   =       /usr/lib/php4

;; Global PHP defaults

warn_plus_overloading   =       On      ; warn if the  operator is used with strings
track_errors            =       On      ; Store the last error/warning message in $php_errormsg (boolean)
track_vars              =       On      ; enable the $HTTP_*_VARS[] arrays, where * is one of

magic_quotes_gpc        =       On      ; magic quotes for incoming GET/POST/Cookie data
                                        ; many people think that the system is a pain in the
                                        ; a**, but it probably does represent a security 
                                        ; feature for in-experienced PHP developers. Turn it
                                        ; off if you don't want PHP to mess with your incoming
                                        ; variables.
include_path    = ".:/usr/share/php"
session.save_path = "/var/state/php"
extension=mysql.so

error_reporting = 15

display_errors = Off

error_log = syslog

log_errors = On

sendmail_path = "/usr/sbin/sendmail -t"


And compile-time configuration:
Configure Command
                                                                                     './configure' '--prefix=/usr' '--with-apxs' '--libdir=/usr/lib/php4'
                                                                                     '--includedir=/usr/include' '--datadir=/usr/share/php' '--with-config-file-path=/etc'
                                                                                     '--enable-inline-optimization' '--enable-magic-quotes' '--enable-track-vars'
                                                                                     '--enable-memory-limit' '--enable-wddx' '--enable-sysvsem=shared'
                                                                                     '--enable-sysvshm=shared' '--with-xml' '--with-gd=shared' '--with-ttf'
                                                                                     '--enable-ftp' '--with-readline=shared' '--with-mm' '--with-mysql=shared'
                                                                                     '--with-ldap=shared' '--with-imap=shared' '--with-zlib' '--with-pgsql=shared'
                                                                                     '--with-interbase=shared' '--with-dbase=shared' '--with-gettext=shared'
                                                                                     '--with-pspell=shared' '--enable-calendar=shared' '--with-snmp=shared'
                                                                                     '--enable-ucd-snmp-hack' '--with-sybase-ct=shared,/usr/freetds'
                                                                                     '--with-pdflib=shared'