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Can't access shared mailbox?

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jab9417
New Contributor

Anyone have any idea why a user wouldn't be able to open a shared mailbox ("Can't expand Folders" error message) in Outlook 2016 or Outlook 365 on a non-domain machine?  The user can access the shared mailbox in OWA just fine, they can access it Outlook 2013 just fine, and if the machine they are logged into is joined to the same domain as the exchange server they can access it with Outlook 2016+ just fine.  But, if they are on a home machine or other machine that's off the domain (even if it is on the same corporate network) they can't access the shared mailbox using Outlook 2016+. 

 

I don't see any GPO or missing certificates that would explain this behavior, and there are no ipsec policies that I can see. I don't get what's happening.  Any ideas?

3 Replies

How exactly is he trying to access the mailbox, as there are several methods? If the issue is only happening outside of the domain environment, it's most likely related to restrictions you've placed on external autodiscover or authentication.

@Vasil Michev  Well, as stated, the users can always access their own mailbox no matter where they are (on or off the network), no matter what the client  they are using (OWA, Outlook 2013, Outlook 2016+), and no matter whether their computers is bound or unbound.

 

What they can't do is access shared mailboxes (same exchange environment) using Outlook 2016+ UNLESS they are on a computer bound to the same domain the exchange server resides in.  computer.  OWA and Outlook 2013 work fine in all cases to access the shared mailboxes (bound to the same domain or not), but Outlook 2016+ does not.

 

That said I don't see how this could be an autodiscover or authentication issue as access the shared mailboxes  works just fine with the other clients.  It seems to be specifically a 2016+ "thing". 

 

Further bit of background in case it helps, but these users are using linked accounts. Their user account exists in one domain, while their mail in another, and there is a bilateral trust between the two domains.  Again not sure that's relevant since it works in OWA and Outlook 2013 just fine, but I thought I'd mention it. 

 

I can also confirm that the users have full control access to the shared mailboxes and the fact that the mailboxes can be opened in OWA and Outlook2013 lead me to believe there are no permission issues between the users and the mailboxes.   

  

@jab9417 Hi Jab, I'm having the exact same problem that you're describing here. A linked account in a subsidiary domain isn't able to access certain shared mailboxes on Outlook versions newer than 2013. They're able to use OWA and Outlook 2013 just fine, but cannot open the box on 2016 or O365 versions of outlook. 
Have you found any solution to this issue yet?