Hi All,

I am currently going through a 2010 -> 2013 upgrade and the 2010 environment has the ambigious namespace problem. As part of the 2013 upgrade we are moving to a new namespace anyway so I didnt think this would be a problem but I am experiencing some strange issues with Outlook after moving test users from 2010 -> 2013.

Problem 1 - Some users when their mailbox is moved they get a prompt in Outlook telling them an administrator has made a change and they need to close Outlook, which is fine I expected that with the new namespace but then after they re-open Outlook they are then getting the prompt a 2nd time and only then after closing and re-opening twice are they able to access their mailbox without any further prompts.

Problem 2 - Some users when their mailbox is moved are unable to Open their mailbox for up to 1 hour, Outlook opens and hangs for several minutes before giving a message that the folders cannot be opened. you can try this several times and eventually it will open. This makes me think Outlook is not getting the correct information from Autodiscover at that time to tell it that the users mailbox has moved.

Ok so now here is the environment details:

• Exchange 2010 Namespace - mail01.contoso.com which resolves to LB for 2010 environment
• Exchange 2013 Namespace - mail02.contoso.com which resolves to a different LB for the 2013 environment.
• Autodiscover.contoso.com resolves to the LB for the 2013 environment.
• Outlook Anywhere on 2010 servers external URL is set to mail01.contoso.com
• Outlook Anywhere on 2013 servers internal & external URL is set to mail02.contoso.com
• NTLM Auth is configured on both with the IIS Auth set to Basic & NTLM as per Microsoft documentation

I should also mention that it is a multi-domain single forest AD with the Exchange 2010 servers deployed in subdomain.contoso.local and the Exchange 2013 servers deployed in the root domain contoso.local

I'm struggling to see what could be wrong and why the mailbox moves are causing so much of a headache, any recommendations and ideas welcome.

Thanks

• Edited by AndyHeywoodMCSE Friday, February 20, 2015 9:04 AM Additional Info

This kind of transition works a whole lot better if you switch all client access to go through Exchange 2013 CAS before you start moving production mailboxes.