How do I prevent one of my email accounts on Outlook from sending emails to a particular email?

I have two acounts at work. When I send emails and copy in my boss, from one of my acounts, I need to always use his corresponding email. I keep on using the wrong email by mistake. Is there a way of blocking your acount to not be able to send to certain addresses?

I would appreciate any help regarding this. 

Thankyou