Blocking external email for one user

IDK the business reason for doing so but I’ve received a request to block the exchange of external email for one user. There is one user they do not want any of their sent email to reach external people, nor, if any external people send them email do they want it received by that person.

Is there some way to do so?

Subject: Re: Blocking external email for one user

Hello Rob!

On the document below you can find related information to restrict a user (or some) to send external mail:

Restricting users from sending Internet mail
IBM Documentation http://www-01.ibm.com/support/knowledgecenter/SSKTMJ_8.5.3/com.ibm.help.domino.admin85.doc/H_RESTRICTING_WHO_CAN_SEND_MAIL_TO_THE_INTERNET_STEPS.html

Best Regards!
Rodrigo