First, assign the "Shared mailbox" signature (with text values) to the shared box.
On the platform side, in the "Team" tab, add the delegation of the signature to all members of this shared box.
On the Outlook email client side, when editing a new email, by changing the "From", point to the shared mailbox. The signature of your main account should be displayed by default.
When opening the Add-in, you will have the possibility to choose a delegated signature, the one of the shared mailbox.
#Shared box #Shared #Delagated signatures #Delagated #Addin #Add-in