PHP Mass emailing

Question

I work for a small marketing company that has asked me to develop a PHP application to send emails for their company without getting blacklisted or emails showing up as spam

Answer 1

A company I work with has had success using an Open Source (LGLP license) project called PHPMailer for a similar function -- maybe this would be a good start for you?

EDIT: PHPMailer is great software but I spoke too quickly. I meant to say phplist.