onsakia

I get an error message that the system can not send a mail when i am closing the task of a user. The warning i get is : Warning: mail() [function.mail]: SMTP server response: 550 5.7.1 Unable to relay for [email protected] in C:\Program Files\xampp\htdocs\nacchelp\common\common.php on line 2490. Please, can somebody help me over this error. I am attaching my common.php configuration file. I am running the system Win XP, Apache, MySQL 5 and the version of the system is 1.7.2.0