User can't sign in or sees the wrong interface after a mailbox move in Exchange Server 2013 or Exchange Server 2016

Applies to: Exchange Server 2016 Enterprise EditionExchange Server 2016 Standard EditionExchange Server 2013 Enterprise


In a co-existence environment, you successfully move a user mailbox from Microsoft Exchange Server 2010 to Microsoft Exchange Server 2013 or Microsoft Exchange Server 2016. However, when the user tries to sign in to the mailbox in Outlook Web App or Outlook on the web, the user receives the following error message:

You weren't able to sign in because the mailbox is being moved. You won't be able to access until the move is complete. Please wait and try again later.

Additionally, if the user can sign in to the mailbox successfully, the page may show the interface of Outlook Web App for Exchange Server 2010. 


This problem occurs because the client and the Outlook Web App application pool on Client Access servers (CAS) in Exchange Server 2013 or Exchange Server 2016 keep the cookies that are generated by Exchange Server 2010. Therefore, the user is proxied to an Exchange Server 2010 CAS.


To work around this problem, use one of the following methods.

Method 1

Have the user wait at least 30 minutes after the mailbox is moved before they sign in to Outlook Web App or Outlook on the web. 

Method 2

Clear the cookies on the client and on the server that is running Exchange Server 2013 or Exchange Server 2016. To do this, follow these steps:

  1. Clear browser cookies on the client.

    Learn about how to delete cookies in Internet Explorer.
  2. Clear the cookies on the server. To do this, restart the MSExchangeOWAAppPool application pool by running the following command on the server:
    Restart-WebAppPool MSExchangeOWAAppPoolnull