Why does Drupal think my email address is invalid?

I'm trying to send an e-mail from a module I'm writing, but I keep getting this error message, even when I hardcode a valid addre开发者_StackOverflowss in the call to drupal_mail():

Warning: mail() [function.mail]: SMTP server response: 550 The address is not valid in DefaultMailSystem->mail() (line 77 of C:\Program Files (x86)\wamp\www\drupal-7.0\modules\system\system.mail.inc).

How do I fix this?

---

This has nothing to do with Drupal but with the SMTP (simple mail transfer protocol) configuration in php.ini file somewhere in C:\Program Files (x86)\wamp\ (I don't know exactly where because I use xampp). There you have to look for 'mail function' where you can put SMTP = smtp.server where server is the name of the server from your internet provider. Personnaly I don't change a thing to this because everything will work once going live.

---

What about using your own smtp server with the SMTP module ? Gmail allows you to use their SMTP server and it will save you the complexity of setting up a local SMTP (especially on Windows ;) )