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Outlook 2016 error when trying to open mailbox

I wanted to share some information for the people finding this post through search engines and are having the same problems I had.

Using Exchange 2010, when upgrading a certain user from Outlook 2007 to Outlook 2016 the user could no longer open his mailbox.

When opening Outlook 2016 in cached mode I would get the message:

Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The file <path>.ost is not an Outlook data file (.ost).

When opening Outlook 2016 without cached mode i would get message:

Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. Network problems are preventing connection to Microsoft Exchange.

However, the mailbox could still be opened in Outlook 2007, and through the browser using OWA.

All mailbox permissions were default, and OWA, ActiveSync, MAPI were enabled.

When adding the profile the ActiveSync settings seemed to be in order because all information was detected automatically.

Other users on the same Exchange 2010 server didn’t have any issues.

Other users on the same computer didn’t have any issues.

Recreating the Outlook profile didn’t make a difference.

Trying on both Windows 7 and Windows 10 gave the same result.

In the “C:\Program Files\Microsoft\Exchange Server\V14\Logging\RPC Client Access” server log files I noticed an error message every time the user tried to start Outlook:

RpcDispatch: [UnknownUserException] Unable to map userDn ‘/o=Exchange Organization/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=Mailbox 123 – Example username 123’
to exchangePrincipal (StoreError=UnknownUser) -> [ObjectNotFoundException] The Active Directory user wasn’t found.

When checking the legacyExchangeDN of the user through adsiedit I noticed it had a trailing space at the end of the name:

‘/o=Exchange Organization/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=Mailbox 123 – Example username 123 ‘

After removing the space at the end of the legacyExchangeDN and recreating the Outlook profile the mailbox could be opened again.

May 18, 2017 at 17:01
1 comment »
  • August 10, 2017 at 06:57Steve

    Yes, thank you – spent hours trying to track this one down!

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