I recently setup a shared mailbox in my Office 365 subscription so that a few people in my company can have access to mail sent to a generic company email address without the need to use an Office 365 license. I found that I wasn’t opening up the mailbox frequently and hence wasn’t getting notifications of any new mail that was being sent to it. Any mail sent to this address was getting overlooked. At this point I decided to setup a forwarding rule to my own mailbox and discovered it was slightly different from the steps described in the Configure email forwarding in Office 365 Microsoft support article as these user options were disabled & grayed out for my shared mailbox:
It is still possible for shared mailboxes and regular mailboxes to be forwarded to another mailbox by using the Exchange Admin center directly by following these steps:
1. Login to the Office Admin center using an Exchange privileged tenant account
2. Open the Exchange Admin center
3. Select mailboxes
4. Select the mailbox under the shared tab and click on the edit button
5. Go to: mailbox features –> view details under “Mail Flow”
6. Set your forwarding options by enabling forwarding and selecting your mailbox. At this point you can also choose if you want to leave the message in the shared mailbox.