You can use either the Rejoiner Customer ID or the customer's email address.

PUT /customers/CUSTOMER_ID/tags/

PUT /customers/tags/by_email/?email=CUSTOMER_EMAIL

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Any existing tags not included in the payload will be removed from the customer.

Payload Specification

Param Name	Required	Type	Description
`tags`	Yes	Array(String)	Tags to be applied to the customer
`start_journey`	No	Boolean	A value of `false` will optionally prevent the modified tags from triggering any journeys. Defaults to `true` if no value is passed.