A client of mine has set up about a couple dozen auto-responders, each of which serves a single document upon request. I'm looking for a script, preferably PHP, that will handle this automatically. Perhaps something where people write to "documents@my-domain.com" with a subject line like "Request Document #5".

Any ideas? I've tried Googling it a few times, but my keywords are all too common to do any good.

Thanks! -Jonah