"The Microsoft Exchange Administrator has made a change that requires you quit and restart Outlook"

I changed the delivery options on the exchange server to automatically forward the user's email to an external email address.  Whenever I do this, the user gets the "The Microsoft Exchange Administrator has made a change that requires you quit and restart Outlook" message and they are not able to receive any messages. Once the user restarts outlook, they are fine.  This happens every time I configure forwarding for a user via the delivery options on Microsoft Exchange.  Does anyone know why the users are getting "The Microsoft Exchange Administrator has made a change that requires you quit and restart Outlook" message whenever forwarding is configured for the user via the delivery options on Microsoft Exchange?