How to Restrict Outlook to send mail only within my company domain

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Is there a feature, rule, tool, add-in, or macro that will ask me to
confirm before I send email outside my comany? On more than one
occassion, I meant to send private messages to (e-mail address removed)
and outlook autocomplete sent it to (e-mail address removed) instead.

So is there a way to prescan outgoing messages and pop up an 'are you
sure' message box if there is any addressee not in the mycompany.com
domain?

Thanks in advance for any hints.