Configure Network Access for the MassTransit Services
Configuring the MassTransit services to have network access will allow you to set remote mailboxes for your contacts.
If you want to set remote mailboxes for your SFTP Client Contacts, you need to grant network access to the MassTransit Transporter service. If there will be remote mailboxes for any other contacts, you need to grant network access to the MassTransit Engine.