At this time I am not aware of any functionality in Constant Contact which would add this second step required to confirm an unsubscribe.
The current Constant Contact flow asks for a single confirmation when the user click on the unsubscribe link and does not have an option to send a confirmation email. I am also not aware of any plans to implement this option in the near future.
If you have any questions or if we can provide any more information, please let us know!
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