Auto Responder / Newsletter mod

Has anyone developed an autoresponder mod that uses the exiting dolphin database of users as they stand not exported to another db or table

I am looking for a mod that can send time based emails I.e welcome message on day 1, follow up day 3, membership invite day 5 etc

have a look at these 2

http://www.boonex.com/m/automailer 

http://www.boonex.com/m/auto-mailer 

Thanks i will investigate these products further :)