What is the simplest way to set up “reply to this email directly”?

[ZennedStainna]

I have a site that people communicate via private message.I send npemail notifications to these people.In the email notifications, I want the user to be able to hit reply on the email. My system would then analyze the subject line and write the message to the database for that user.I have an email server set up (followed instructions to install dovecot and postfix). However, its a very basic set up and I'm completely clueless how to implement the system I just described.I'm looking for a good overview answer or a link to a tutorial that goes through this.