I'd like to automatically respond to emails with a specific subject. Generally, how's that done? Is there an email reader that I should use that will simplify this task?
Not a problem, do you have any specific questions about IMAP? I used those functions about 5 years ago for a small support ticket project, but wouldn't mind trying to help you.
One thing to keep in mind, since this is an email account you use and not an automated one, if you are using POP3 for your email connections, this setup is going to be 50/50 at best. You and the system need to both be using IMAP to ensure you don't remove a file from the server before it gets processed by your script.
Have you every looked at the SwiftMailer library This is the component library used in many of the frameworks. It has great documentation and is very stable and secure.
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