If a Hubspot contact has multiple email address will GrowSurf sync participant data to all of them?
Each contact within a Hubspot account is uniquely identifiable by their primary email address. Similarly, each participant that is added to your GrowSurf campaign is uniquely identifiable by their email address. When GrowSurf either adds a new primary contact or updates an existing primary contact within a Hubspot account, only the email address associated with the GrowSurf participant would ever be updated to include GrowSurf participant information.
GrowSurf will never read any contact data from your HubSpot account and consolidate only push information from GrowSurf to Hubspot. The relationship between GrowSurf and Hubspot is one-to-one. One GrowSurf email to one Hubspot email.