multiple mails problem

First, I want to thank whoever takes this on ahead of time. I'm just starting to learn php and I had a problem with sending the mail to multiple users , when i send an email to some users it shows their email addresses to everyone. I do not want the people receiving the email to see everybody elses email address that is on the list. My Problem is : i want send the same mail to multiple users ,these mail ids are collected from the database and concatnated with each other by separating them with commas and i was used the mail function as mail($to,$subject,$message,$headers) where $to='nn@yahoo.com,yy@rediff.com,...'; But my intension is "I do not want the people receiving the email to see everybody elses email address that is on the list." If i can use Bcc then only 2 mails goes i.e., to and bcc . I don't know how to solve this problem, Please help me anyone Regards Narayana narayana@itex-world.com