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Hello,
Our company is in the midst of an email migration. One issue we are having is when users would like to view multiple mailboxes in Outlook. Example, setting up the first account: ******@companydomain.com, works perfectly fine in Outlook. Second account: ******@companydomain.com, loaded fine as well, even though both accounts use the same server. We can see both accounts and folders on the left-hand side. However, when you try to access the second account, the user is receiving this error: Cannot expand the folder. The set of folders cannot be opened. The attempt to log on to Microsoft Exchange has failed.
Using Classic Outlook on Windows for personal email, calendar, and contact management
Locked Question. This question was migrated from the Microsoft Support Community. You can vote on whether it's helpful, but you can't add comments or replies or follow the question.
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Does the first account have permission to open the second mailbox? It sounds like permission problem. Go to https://admin.exchange.microsoft.com/ and open the 2nd mailbox. Click Delegation tab and click Edit button under (Full Access).