Hello @crackyflipside,
In short: Both options work, but with a different tradeoff.
Connector
The connector can be used but you won’t be able to fetch the attachments (per current state, as of today, september 2024) via the connector.
The elements you need to connect are the same as for the External Transform: You need a client_id, client_secret, tenant_id, and the shared mailbox you want to connect to.
To what I recall, you should use the MS Graph mode in Schema field.
The setup on Exchange/Microsoft side is the same as the External Transforms post (need the Mail.Read permission, etc.)
External Transforms
The thread that you posted is still relevant. The External Transforms approach might be more flexible, as it can fetch the attachments of the emails.
See the thread for more information.
Both
You could use the connector to fetch the emails and the metadata of the attachments, and then you could use an external transforms to only fetch the attachments !
Hope that helps !