mailing list program

Hi All, I want to send an email to users located at a database containing like 50,000 records. I may do that by looping through the records and mailing each of them, but this would take long time to finish, and most probably the script will timeout before it finish. So my question is how to do such a thing ? I know its related to mailing lists programs, any hints ? or do you know of any free mailing list script that can connect to a database and read the email field and send preformated emails ? Thanks Ahmed