Multiple Addresses Mailer

Hi All I am creating a mailing list system in which I should be able to broadcast a message to multiple recipients I am using the mail() function and putting all the recipients names in the "to" argument separated by commas. When I do this the mail goes to all the people but they come to know that it was sent to others as well. I want to be able to send mail so that each recipient thinks that this mail was ONLY sent to him/her. Thanks --pS Pushpinder Singh Garcha