Rule based on count of Recipient=1 only

Hi, I need some help to create a policy/rule that only generates an alert based on only 1 recipient whereas the recipient can be any domain.

I found a similar thread but this seems to feature multiple recipient/domain count mechanism. My requirement is to craft only based on 1 recipient only within the email.

Thank you for the response in-advance.

Reference:https://www.symantec.com/connect/forums/rule-based-count-recipient