mail() problem

Hi! I just bought a dedicated server with a LAMP (Suse 8.1) system preinstalled. Everything (including PHP) is working fine, however PHP's internal mail() function does not seem to work. I created a testpage that only takes the recipient as form input, everything else is hardcoded. The page works perfectly on my local testserver, but it does not work on the new machine. I verified that sendmail is in the correct postion, I also successfully sent an e-mail from the command line using sendmail, but whenever I try to send an e-mail via my PHP page it does not work. After submitting to the page, the result pages (that sends the e-mail) appears immediatly. I checked the log file /var/log/mail that normally contains an entry when an e-mail is sent, but nothing appears in there when I try to send the e-mail via PHP. Do you have any ideas what could be wrong? Thanks, Matthias