Shared mailboxes you have access to are automatically added to your folder list when Outlook starts. After being granted access to a new shared mailbox, simply restart Outlook. The new mailbox can then be found in the folder list:
Permissions can take up to an hour to reach all systems. If you don’t see the newly added shared mailbox, wait an hour and restart Outlook again.
Additional Information
For additional information on using shared mailboxes, please see the following Microsoft documentation:
Open and use a shared mailbox in Outlook (microsoft.com)
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