A good PHP auto-reply system

Can anyone reccomend a good PHP (or perl) Web-based email auto-reply thingy. I work at a company that hosts websites and provides POP email accounts, and i'd like to allow our clients to come to our website, log into a "clients" section and have more control over their service... I'd like to allow them to specify email accounts as "away" and provide a little "i'm on vacation" type message, and a date range associated with that message. anyone know of any *free* or cheap it's a SOSB (small office, small budget) software that will allow users to create an auto-away message? If i dont find a nice one, i'll probably end up writing my own... but i'd prefer to save myself the work of reinventing the wheel if i could possibly find a good free one and work on hacking the code for my own needs.