When I add a Outlook profile of mailbox A using my user account mailbox B, Outlook resolves that name of mailbox A. When I open Outlook to login as mailbox A, I get the following error, in Outlook before it closes:

"Cannot open your default e-mail folders. You must connect to Microsoft Exchange with the current profile before you can synchronize your folders with you Outlook data file (.ost).

When I take off cache mode, I get:

"Cannot open your default e-mail folders. Microsoft Exchange is not available. Either there are network problems or the Exchange computer is down for maintenance."

Note, I have granted myself full mailbox rights to Mailbox A. I have the profile enabled for Outlook Anywhere. I am in co-existence with Exchange 2010 and I have no issues connecting to mailbox that reside on Exchange 2010 mailboxes but I cannot connect to different Exchange 2013 mailboxes using my account.

Hello,

From the first error, your ost file seems be corrupted. I suggest you recreate your outlook profile to check the result.

I don't recommend you put two exchange accounts into a outlook folder.

Please create different outlook profile for mailbox A and mailbox B to check the result.

I already tried removing the OST file. It seems to be a configuration issue on the server side. I can connect when I log in as the user mailbox A but not with a different user accessing the mailbox A.