When you have a subscription, you can click "I am interested" and it will send an email to the post owner, and put a message on their dashboard. Then they can email you. Also, every one has a profile they can put all their information on, here is mine: https://bidpeek.com/profile/Michael

It's still really early, I only spent a few days building it and have a lot of ideas.

Edited to add: When you click "I am interested", you can also append a message to send.