Serving missionaries email address

How do I update the Serving Missionaries email addresses? I understand the assigned missionaries are updated by the local mission office. But what if I want to change the email address for a missionary from our ward? I can't find how to do that...

If it's a MyLDSMail.net email address, it's automatically assigned by the Missionary Department when the call is issued. It cannot be changed except by request. The missionary can contact their mission office if such action is necessary.