Strange pblm with email addr being modified only when you send

When we copy a list of emails from 1 email and then paste them into a newly created one it looks ok but when we send the email it adds OU= or O= to the end of each email that is not a domino email. For example…

“Boc Hou” <bhou@acorp.com/OU=, “Gordon Case” <GCase@acorp.com/O="

What would cause the addition? This only seems to happen when we copy and paste into a new email.