I have had MS Office 2011 outlook setup on a MacBook Pro for over a year, connected to a Hosted exchange server.  I have 95 users connected to this hosted exchange server and all are windows, except for this one.  The connection to the server is solid, but when the MAC User sends an email it will sit in the outbox for 5-10 minutes.  This does not happen with any windows or Ipad/Iphone/Smart phone users.  This also happens at the office and home site as well.