Hello, Contacts who have opted out of receiving all mails and have been placed on Do-Not-Mail list must opt themselves in. The account owner cannot add a contact in Do-Not-Mail list back to a different list. The action must be initiated by the contact. When using the API, that means that the <OptInSource> must be ACTION_BY_CONTACT, which can only be used when the API call is the direct result of an action performed by the contact (e.g. clicking a Subscribe button in an application). It is a serious violation of the Constant Contact Terms of Service to use the Opt-in features of the API in any other way (i.e. opting in a contact without his or her action and consent). In order to opt-in a contact, you must take the contact's detail data and modify <ContactLists> to include the contact contact lists in which the contact is signing up. Then, you use the PUT method to apply the change against the contact resource.
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