Add contacts without duplicating them.
Paste addresses into an audience or assign audience IDs when importing contacts. Existing members retain their original join date when added again.
Synchronize the cohort you mean.
Public audiences use static membership. If your CRM or warehouse calculates a segment, synchronize both additions and removals. Changing a contact property alone does not recompute the list.
Treat eligibility as a separate check.
A channel label indicates a stored identifier, not consent or reachability. Removing a contact from one audience leaves the contact and other memberships intact.