It is possible to withhold trigger communications for reservations originating from a channel. For example, Airbnb collects the guest payments and remits the host payments to the property manager. Thus, most property managers do not want their remaining balance due trigger being sent to an Airbnb reservation.
Select the channel you wish to exclude from the drop down under "Don't apply triggers to the following channels." It is possible to exclude more than one channel by adding multiple conditions to the trigger.