Free/Busy not working in Outlook & OWA


We have an Exchange 2010 environment, and we have the servers distributed on 3 regions/datacenters, all of them are installed in the same forest.No cross forest.

The issue is with a single user mailbox that which ever region server it is on, it can't see free/busy for other people that are on the other 2 regions. Issue is ocuring in Outlook and OWA as well. All servers are configured the same, we checked the EWS, IIS logs, no error.

The error that the user's get in OWA is "The Attendee  server couldn't be contacted. (Error code:5016)".

We even create a new mailbox and connected the AD user to this new one, but the issue still persists.

Does someone have any suggestions/ideas what can be the cause?

Mihai Calin VingaAsked:
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Michael B. SmithExchange & Active Directory ExpertCommented:
This is a simple guess - are the userprincipalname and primary SMTP address out of sync? That is, not the same value?

Along the same idea thread - is the upn suffix of the affected user one of the domains contained in the Exchange SSL cert?

One more idea on that thread - is the upn suffix properly defined (if different from the name of the forest)?
Mihai Calin VingaAuthor Commented:
Yes, I check, UPN is properly defined. Has the same value as SMTP address.
Michael B. SmithExchange & Active Directory ExpertCommented:
And the other two questions?
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Mihai Calin VingaAuthor Commented:
Both yes, the UPN suffix  domain is contained in the Exchange SSL cert, and is no different from the name of the forest.
Michael B. SmithExchange & Active Directory ExpertCommented:
Other users work ok? Just this one user is experiencing the problem?

If so, I would do something pretty old-school. Use your favorite tool (ldp.exe, adsiedit.msc, dsquery, get-adobject, etc.) and dump all the properties of the user who is failing and one who works. Compare and contrast.

I wonder if this might be an adminCount issue (see a blog I wrote lots of years ago on the topic: adminCount, adminSDHolder, SDProp and you!). You might check that attribute first. Exchange has traditionally had interesting challenges with admin users.

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Mihai Calin VingaAuthor Commented:
Yes, there's just a user who is facing this issue. I will  compare the AD attributes, Monday, and I will let you know about the results.
It's a very strange issue, because for this user mailbox,  free/busy is working with users in the same region, but not in the other two (as I said, we have servers spread in three regions). We even moved the mailbox on another region, but it's the same.
Michael B. SmithExchange & Active Directory ExpertCommented:
Author did not reply after several comments and requests for additional information. It seems likely the comments from me allowed the author to resolve the problem.
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