There are a couple of ways an existing Trade user/profile can connect to a Marketplace-enabled organization.
By invitation(see additional articles below)
On the Marketplace Trade dashboard, Vinosmith will show a list of other Distributors if that contact has the same email address
The contact address matches the organization's Allowed State / Zip Code Fencing setting
When a trade user logs in, they are offered to connect with other organizations if 1 or 2 criteria are met:
This other Distributor has an account contact using the same email address as your organization. If I’m a buyer with Distributor A and I'm not yet linked to Distributor A, I can connect to Distributor A. Since emails are unique, we automatically recognize it's the same user.
The other organization has a list of whitelisted States where they can sell.
In both cases, the display looks like:
When a buyer connects with your organization, the email addresses listed in the marketplace.request.to.connect key in the Outbound Email section of the Admin panel is used.