How to add Office 365 shared mailbox to Apple Mail App?

Hi all,

I'm trying to add a shared mailbox to my Apple Mail application however. I can't get this to work.

Our parent company holds multiple domain names and so I have a email account for multiple domains.

I followed the official Microsoft guidelines found online only I can't get it to work.

Does anyone here have a solution?

Microsoft article I found:

https://answers.microsoft.com/en-us/msoffice/forum/all/sending-from-a-shared-mailbox-in-office365-via/b03e5d02-1dbc-4a95-8cfc-3c0c82a1d5b2?auth=1

Hope someone knows a sollution