Email Address is not a valid bcc address when using REST API to send Activation Email

Hi, I have integrated a external environment with Shopify and I am using this REST API to send activation emails to customers. However, I have a requirement to add bcc email address in the activation email as well. I used the same REST API above to add bcc email address in the activation email but for some bcc emails address I am receiving the error abc@example .com is not a valid bcc address. I have checked the format and validity of the bcc email address. My intuition is that a bcc email address must be associated with a Shopify user. I tested this theory by suspending a user and adding his email address in the bcc and it failed with the same error. I activated his user and tried again and activation email was sent bcc successfully. Am i correct? Is this error happening because when a email is not associated with Shopify user account or am i missing something else?

Hey Muhammad,

If you use the GraphQL equivalent do you see the same issue? ie: customerSendAccountInviteEmail - GraphQL Admin