One email to forward to multiple email addresses

I am looking to create one email (example@domain.com) to forward to all email addresses in a database.

People can email to example@domain.com, and then that email would get blasted to a list of predefined email addresses. It would need to include support for attachments.

I realize this is not secure at all and leaves this email address open to anybody to use, but this is what our organization wishes to do.

What would be the best way to do this on a PHP server?

Thanks.

While Arthur's answer made sense and most likely would work, I ended up finding that my host had the feature I was looking for buried deep inside it. For those who were wondering, it is called discussion lists.