migration from SBS 2008 exchange 2007 to exchange 2013

I have an issue with the migration.  I have moved a few users to a the new 2013 exchange server. I can access the mailbox on 2013 viahttps://ex2013/owa internally and send and receive emails but I cannot get outlook 2010 to connect to the mailbox on the exchange 2013 server.  Outlook 2010 gets stuck on Logon to server during autoconfig of mailbox and I get prompted with username and password for the mailbox but nothing works. I have setup exchange proxy detail within outlook manually and still no joy :( 

Ive been following this procedure

https://blogs.technet.microsoft.com/meamcs/2013/07/25/part-1-step-by-step-exchange-2007-to-2013-migration/

Any help would be great!

Ben