Under GDPR guidelines, contacts can opt-out of tracking their behavior. Behavior tracking includes opens, clicks, forwards, shares, clickstream, and Google Analytics. This can be done via form (Subscribe Form or Preference Center), one-off updates, data imports, and API.
How Would Tracking Preference Impact Drip Campaigns?
Those contacts that opt out of tracking (tracking is set to "Not Allowed") will not have their behavior like opens and clicks tracked for the sake of analytics, triggers, or automation. If included in an automation that uses flag events or wait for events based on behavior, contacts without tracking will appear to NOT have taken action.
For example they would fall into the "Did Not Open" or "Did Not Click" track even if they did as we are not tracking their behavior.