Warn before sending emails to external domains in Outlook

Question

How can you get Outlook to warn you if you are about to send and email to an external domain?

Sending large amounts of emails everyday it is always possible

Answer 1

I found two add-ins for Outlook that does the same if you don't want to use VBA,

• www.safesendsoftware.com and
• www.sperrysoftware.com.