smart BCC feature is made for that , it helps adding communication from other email accounts to a deal. You will need to register your domain though which is not possible for Gmail in your case but for other domains that you own you can do that.
It would be great if there is a feature/button on the "mail" section where you can click and it will find or suggest deals without opening the email. I have many many many deals, which the mail isn't detecting automatically. THis is one of the useful feature of pipedrive but unfortunately, it seems it hasnt been optimized properly.