Hi,

I have deployed Exchange 2013 co-existence with Exchange 2010, Currently doing migrations and now we are getting below error. When I try to access other user mailbox (B) from Account (A) which is having full permission on mailbox B.

I tried by reset attributes and inherit permissions but, issue still persists....

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X-OWA-Error: SDServerErr;Microsoft.Exchange.Data.Storage.AccessDeniedException
X-OWA-Version: 15.0.995.28
X-FEServer: ZAJNBEXC11
X-BEServer: zajnbexc05.cws.sasol.com
Date: 2/4/2015 6:27:12 AM

This issue has been sorted out in this earlier discussed thread @ https://social.technet.microsoft.com/Forums/exchange/en-US/509c9a5a-41b0-4dcd-80e7-1d26b09edc47/unable-to-access-user-mailbox-with-full-access-permissions-through-owa?forum=exchangesvrgeneral

you need to apply mandatory properties on one of the mailbox.

Run this command : Set-Mailbox UserName -ApplyMandatoryProperties

The possibility could be msExchVersion attribute is not proper in AD ?By the way, when need to migrate users mailboxes from old server to new one, you may also consider on this automated option (http://www.exchangemailboxmigration.com/) that can be a good help to get this job done in more hassle-free manner.