autoresponding email

im looking for an email program that will auto-respond from templates based keywords found in the subject and/or body of the email.

Or another way to put it… conditional reply
replies are based on preset conditions

and yes outlook 2007 (and thunderbird) can do this, but the steps are so tedious to set up a reply it can get rather dull when trying to set up 100+ replies with different sets of keywords

btw, is there an automater that will speed up that process for outlook 2007 or thunderbird?

preferences-
free, uses an external imap email address,
open source is an option

the operating system doesn’t have to be limited to windows, im open to mac and linux suggestions too

thanks
-NWT