A Plugin that can analyze emails

My site has quite a lot of posts that are individual listings (example: real-estate listings). So the way the site is designed we can create a separate post (by just filling out a form) and it will create a listing. Some of my clients don’t want to login every time when they want to make changes to their listing. I was wondering whether there is a plugin or another way to change the desired info using an email.

So for example, lets say Client “A” creates a listing with us. He/She wants to change the day/time of the open house (at times this needs to be updated daily) remotely without logging in. We create a special secret e-mail address dedicated to that listing where the client can email and update the time. Is there such a plugin where a certain part of a standardized post can be modified?

Cheers