Adding CC watchers

My users want to add cc’s to a ticket, these users don’t necessarily have
rt accounts nor do they need them but here everyone assumes the
@example.com since all our mail servers do. And the RT CC ticket
modification form rejects email addresses with out @example.com how can I
easily change it to assume @example.com if there isn’t one entered?

John

<>< Proverbs 3:5 “Trust in the Lord with all your heart and lean not on
your own understanding;”