new customer registration error

[trepana]

I have just installed oscommerce and when I try to create a new customer I receive the following error:

 

Warning: mail(): SMTP server response: 501 5.5.4 Invalid Address in C:\hshome\virtuals\fierecillas.com\catalog\includes\classes\email.php on line 500

 

Warning: Cannot modify header information - headers already sent by (output started at C:\hshome\virtuals\fierecillas.com\catalog\includes\classes\email.php:500) in C:\hshome\virtuals\fierecillas.com\catalog\includes\functions\general.php on line 29

 

I have read that I have to change something in php.ini, but I don't have this file anywhere.

 

Can anybody tell me the solution?

 

Thanks