Mail Help

[Anon]

I can't get mail to work on my local linux box. When I execute something like this...
<?php
$mailtest = mail("[e-mail]","Test","Test Email");
if(!$mailtest) {
echo("An error occurred.");
} else {
echo("Mail sent successfully.");
}
?>
it prints out "Mail sent successfully.". However, I get this error on the system:
Diagnostic-Code: SMTP; 550 rejected: cannot route to sender <apache@alderaan>

Anyone know how to configure sendmail? Or at least point me in the right direction?
Thanks in advance.

[Anon]

Note: This has to be some sort of php or sendmail configuration problem. I am successfully able to send mail via command line through sendmail.

Thanks again.