urgent: how should php.ini be?

Hi, I am having trouble with sending email by mail() func. of php. I used mail() previously, so I don't think I have a syntax problem. I guess the problem is with my php.ini file. Our webserver and mailserver are different machines. PHP runs on webserver machine. When I send an email with To: somename@ourowndomain.com it reaches successfully. When I try to send an email to the outside of our domain it fails. Using this clue I think there may be two problems: 1 - Messages don't reach to our mail server at all. (May be messages into the LAN reach cause they don't need the mail server.). 2 - Messages reach to the mail server, but the senders name is not in the mail server access list. So, how do you tell php where a mail server is? Or what else can be the problem? You will probably tell me to change the php.ini file, so I put the related part here: ------------------------------------------------------- [mail function] SMTP = oguz@planet.net.tr ;for win32 only sendmail_from = oguz@planet.net.tr ;for win32 only sendmail_path ;for unix only, may supply arguments ; as well (default is sendmail -t) ------------------------------------------------------- Don't tell me that I need to assign "/usr/sbin/sendmail -t" or "/usr/bin/sendmail -t" to sendmail_path, because I tried those too. I spent my day on this, but couldn't solve it, thus any help is really appreciated. Oguz.