You are a delegate for another user's mailbox The shared folder appears in the navigation pane under the Shared heading. On the Type pop-up menu, click Calendar, Address Book, or Inbox, and then click OK. If you have multiple Microsoft Exchange accounts, on the Account pop-up menu, click the account that you want to use to open the other user's folder. Type the name of the person who granted you access, click Find, click the person's name, and then click OK. On the File menu, point to Open, and then click Other User's Folder. If another user has shared an inbox, primary calendar folder, or primary contact folder with you, use this method to open the user's folder. Outlook for Mac does not support Auto-mapping of shared mailboxes.
If you do not have 'Send As' or 'Send On Behalf of' permissions for the account, email from the account will not be sent. This lets you select the account in the From field regardless of whether you have permissions to send from this account. When you use any of these methods, the shared mailbox account is added as an option in the From field when you compose emails.
