AutoFollowup 

Follow up with customers, sending them unlimited autoresponders with a personal touch. Administrate all autoresponders from any web browser, adding unlimited letters and unlimited lists.
customers sending unlimited autoresponders personal administrate browser letters customer service mailing program

AFU Plugins 

These scripts combine with Auto FollowUp. AFU allows people to subscribe to the autoresponder by email, but this collection contains a script that will actually answer an email! It will respond to email subscribe and unsubscribe requests.
plugins scripts combine followup subscribe autoresponder collection contains actually respond unsubscribe requests plugins include