Only until Microsoft Outlook has synchronized with the mailbox, that the most up to date data will be displayed to the user.
Use add additional mailbox and you can add it to favorites, but if you then remove the additional mailbox, the favorite drops.
That being said, I was surprised to see all the answers of "you need full access to the mailbox." That's just not true. Get Shared Default Folder(my Recipient, ol Folder Inbox) ' This open the folder in the current window Set my Ol App. Current Folder = my Folder ' This open the folder in a new window ' my Folder.
Click the Close button at the lower right corner of the window.
The main Outlook 2011 email window will appear on screen.
After installing centrally managed signature adding software, such as the Code Two Exchange Rules family, the Pro version or even cloud based Code Two Email Signatures for Office 365, you may need to disable stamping of the messages with personal signatures created in Outlook.
If you are not able to get all users to manually remove their Outlook signatures, some users may end up having two different signatures: one made by Outlook and another added by the signature adding software operating server-side.Various causes can result in this behaviour such as large mailboxes or OST files, or particular add-ins installed in Microsoft Outlook.If reducing the size of the Sent Items folder or disabling Microsoft Outlook add-ins does not resolve the issue, further investigation will be required in the environment to identify why Microsoft Outlook has not synchronized with the Microsoft Exchange server.Your users must be logged on to a domain to which you have full administrative access as they must be subjected to your GPO policies for this solution to work.Organizations working with Exchange Online (Office 365) can also apply this solution if their users are connected to an on-premises Active Directory or Azure AD to which you have full administrative access. Now you are able to set proper policies to remove current signatures in Microsoft Outlook. Of course, you will need permissions to the inbox first.