Hi @Missy Evenson ,
Yes, a shared mailbox can exist in both Classic Outlook and New Outlook simultaneously. When users toggle between Classic and New Outlook, the shared mailbox should be accessible in both platforms.
Some staff have reported that adding a Shared Mailbox to New Outlook removes it from Classic Outlook.
Adding a Shared Mailbox to the new Outlook does not remove it from the Classic Outlook. In the new Outlook, shared mailboxes are added by right clicking the account name and selecting “Add shared folder or mailbox”, shared mailboxes are found under the “Shared with me” folder. You might need to expand this folder to see the shared mailbox. If the shared mailbox does not appear immediately after being added, it may take a few minutes for it to display. Users are advised to wait a bit and then close and restart the new Outlook again.
For more detailed instructions on how to open and use a shared mailbox in Outlook, you can refer to this Microsoft Support article.
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