I am doing some research on this and looking to see if an email is sent through outlook and the address is unsubscribed in Marketo will the email still be sent? How does the outlook plug-in handle unsubscribes?
If the email is sent via MSI in SFDC, it does respect unsubscribe.
In outlook, the plug in is really just pulling the Template, so I believe it is unable to verify unsub settings and will send the email from Outlook, not Marketo.
I don't see specific item in the docs for this
Configure Unsubscribe Footers in Marketo Sales Insight - Marketo Docs - Product Documentation - but this doc seems to confirm my suspicions since Outlook isn't sending via Marketo's SMTP or system.