PHP mail() Not Working [duplicate]

Possible Duplicate:

Troubleshooting PHP Mail

I can't seem to get mail using PHP's mail() function. I am working on my client's dev server, which is running a version of Ubuntu. I installed sendmail using the following command: apt-get install sendmail. After that I went to the php.ini file in /etc/php5/apache2/ and took out the comment for sendmail_path and set it to /usr/sbin/sendmail -i -t. Despite this, I'm still not getting any mail.

It's quite likely that sendmail itself is not set up correctly. Can you receive a test message sent with the sendmail command? E.g.: echo "test message" | sendmail -s "test message" your-email@your-domain.com