Two Exchange accounts mysteriously assigned to same OST file

Question

I have a challenge that I have been fighting for about a year.  We have users that have exchange mailboxes on two different exchange servers (not on the same network, in two completely different locations). 
For the sake of example, lets call the user Mary and her email addresses are [email protected] and [email protected].
I can configure the first mailbox just fine.   The problem begins when I add the 2nd mailbox.  Using cached exchange, the first account creates an OST file called "[email protected]" in the normal, default location.
 Once I add the 2nd exchange account, the accounts box shows that the 2nd account is also using the same ost file as the first account.  In other words, the "Selected account delivers new messages to the following location:" is the SAME
for both accounts! 
When I launch Outlook, the splash screen shows it's setting up the mailbox for the first time, but once it comes up, there is only one mailbox listed, the first one.  I have tried about a hundred different ways of setting this up, and get various
results.  Sometimes I will get both mailboxes in Outlook, but the 2nd mailbox contains the same items as the first.  In other words, it says it's [email protected], but the contents is actually from [email protected].  Other times, I get the "Temporary
mailbox -- your mailbox has moved" dialog box on startup.  
I've tried going into the 2nd account and manually changing the cache mode OST file to a new file, but I wind up with a blank mailbox in Outlook with no folders and it never updates.  The same thing happens whether I use Outlook Anywhere or
not.  I should also note that we have a VPN between two server networks so that server names are accessible without Outlook Anywhere.
This does not just affect "Mary".  It happens for any user that has a mailbox on domain1 and domain2.  I have gotten around the issue in the past by changing the account name for the user on one of the servers, changing the username
"Mary" to "MSmith", for example.  But lately, changing the username on the server for the users doesn't always work.  
I want to also add that when I have managed to get the "accounts" box to correctly show the correct OST files for each account (after adding the 2nd account but before launching Outlook), once I launch Outlook and see that there is only
one mailbox displayed, I look in the accounts box again and see the 2nd account OST file is the same as the first.
There seems to be something about these two accounts that is confusing Outlook.  HELP!  
Thanks.

Answer 1

Hi,
Please disable using Exchange Cached mode in Outlook and start Outlook in Online mode to check whether the second mailbox is shown there.
I suggest we can configure two Exchange accounts in two Outlook profiles respectively. Then check whether the email goes to one mailbox or not.
Regards,
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Winnie Liang
TechNet Community Support
I had tried that before, but wasn't sure of the outcome, so I just tried it again.  I added the second exchange account to the profile, unchecked the Cached Exchange mode, and started Outlook.  Both email addresses show up as "branches"
in Outlook, but they have the same content.  The top one is correct, and the 2nd one says it's the email address of the 2nd account, but all the folders are copies of the first account.  I quit Outlook and go back into account settings and look and
even though cached exchange mode is still turned off, it shows that messages are delivered to the OST file used in the first account.  Weird...
Keep in mind, it's not just this one user or computer.  So it's not about needing to reinstall Outlook, etc.  I think, somehow, it has to do with the username being the same in both Exchange accounts, but I can't pinpoint that being the cause.