1)   Cruise Control - Rapid Mail Responder 1.0
Cruise Control is the fastest tool available for creating personal replies to your overflowing Inbox of messages, because it can automatically formulate a response based on your reply to similar messages in the past.

 2)   Autoresponder and Mailing List Manager 4.1
A free email autoresponder and mailing list management software FMLP. When a visitor fills up a subscribe form on your website, it automatically adds the visitor to a mailing list and begins the followup. Lots of testimonials. Free support forum.

 3)   BeyondResponse 3.5
An opt-in and opt-out email list management tool, BeyondResponse can be used in a large array of applications. You can use it to provide instant product delivery to your eBay and Clickbank customers, plus manage mass sending for product updates.