I'm looking to disable access to personal inboxes but still have access to a shared mailbox. The company is a registered charity and licencing isnt an issue - this is just the access wanted if possible.
All data will be stored in exchange, no on prem data
Technically you are accessing the shared mailbox with your own credentials, so you need to keep the account active. There are certain "workarounds", but they are not supported and go against MS licensing policy, so I wouldnt advise you to go that route.