“MAPI Error” or another error message appears on the screen when the user is trying to expand Office 365 mailboxes or folders.
The user does not have sufficient rights over the selected mailboxes.
To access multiple Office 365 mailboxes, the user should have the following rights:
- The user should be Global Administrator.
- The user should be a delegate with Full Access permission over all the mailboxes that you intend to access in Office 365.
If the user does not have Full Access permission, perform the following steps to assign it:
- Login to Office 365 admin portal in a Web browser.
- Go to Admin à Office 365.
- Go to User à Active User.
- Select the user to whom you want to delegate the full access right.
- Click on “Edit Exchange Properties.”
- “User Mailbox” page opens up. Go to “Mailbox Delegation.”
- Go to “Full Access” and click “Add.”
- “Full Access Picker” dialog box opens up. Select the user mailboxes, on which the delegate user wants to get full access.
- Click “Add” and “OK.”