This is my first post to serverfault, so I hope you excuse me for asking what may seem like an obvious question. I have tried running a few Google searches, but I really don't know where to begin.
Here's the scenario: I have an online application that sends emails on behalf of the users (at their request, of course). The destination server then sends an autoreply. When the autoreply comes in (from a specified address, each time), I want to forward all of the mails from that address to a PHP script that will then do something else with the message.
Here's the catch: the address that I am using to send the message does not actually exist on my server. I basically set the "From" field to email@example.com, even though they don't actually have a user account/email address on my system (nor do I want to create one, for security purposes.) So I will have to somehow create a filter that catches ALL incoming messages from this particular address. Is this doable, and if so, how do I do it? I'm running Dovecot on an Ubuntu server. I know next to nothing about configuring servers, so I'm going to need very specific, step-by-step instructions.