Our client is experiencing an issue where they are not able to open another mailbox even if the user has full access to the account under mailbox delegation. The user would click on the 'Open Another Mailbox" and they receive the following error
The URL shows the following:
https://domain.com/owa/auth/errorfe.aspx?httpCode=500
The problem I have is similar to the following post but my client is also behind a UAG 2010 server, and I cannot change to forms based authentication.
http://social.technet.microsoft.com/Forums/exchange/en-US/9345d396-b5a6-4d26-a498-7d1539f85d13/exchange-2013-owa-http-500-error-when-opening-another-mailbox?forum=exchangesvrclients
The error within the IIS OWA logs shows as follows.
2014-02-04 17:48:04 10.100.2.10 GET /owa/auth/errorfe.aspx httpCode=500&cafeReqId=f9be7757-b123-4ce1-a585-b9c4ef45cd4b; 443 - 10.100.2.42 Mozilla/5.0+(compatible;+MSIE+10.0;+Windows+NT+6.2;+WOW64;+Trident/6.0) https://domain.com/owa/user@domain.com/?offline=disabled 200 0 0 0
I'm running out of ideas on what could be the issue and but our users will need to manage other mailboxes pretty soon.
Edit: I should also add that the permissions are correct as the user can connect to the target mailbox via Outlook 2013.