I'm having trouble when sending emails thorough the mail() function.

I have a script that works perfectly fine for an email address like [email protected] but when the first part of the email is something with a dot like [email protected] it doesn't work and returns this error :

Warning: mail() [function.mail ]: SMTP server response: 554 : Recipient address rejected: Relay access denied in confirmed.php on line 119

I am using real email address but have changed it in the above example.

Any thoughts - I'm not a php master but surely there is an easy way to send emails to address with a 2 part first section??

Thanks in advance Ali