Thanks Derek. That was helpful. I was confused by the samples shown on the documentation page which said “To unsubscribe from specific campaigns”. I guess this should say subscriptions or email types instead of campaigns
In the context of this endpoint, campaigns refers to email subscription types. If you include the id from a specific email type, you can opt a contact out of a specific email type instead of opting them out of all email. You can get the relevant email type’s id using the following endpoint: