In order to add an unsubscribe hyperlink in an email Notification Template, double click on the text box in the email editor that contains the word or words that you'd like to hyperlink as shown below.
Highlight the word or words you would like to hyperlink for guests to unsubscribe.
In the subsequent pop up window configure the TAG as follows in the URL field:
Make sure that the Protocol is set to <other> and the URL field contains "[unsubscribe]"