Why wouldn't you use Scan2Email via Office365? It's a secured/encrypted connection to the Office365 mail server.
You need a dedicated email adress for your MFP (for security reasons). Please note that end-users can add a password to the PDF file to protect the file from unautorized access in case they make a typo.
Then you setup Scan2Email with:
Authentication (username and password)
Also make sure you enable Authenticated SMTP in the email adresses setup.
And if you would like to add a password to the PDF file, press the Email app, then click on the file format (PDF Button) and choose more, then you'll see options as below;
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The best option would be to scan to folder. Although you don't have a computer that is always on, I would considering leaving one on so the scans can be saved. The Xerox App Gallery does have an Office 365 app (LINK HERE) that will scan documents to your account, but it does require a subscription.
bye for now.
Edit : I'm wondering whether to use Azure Files as there isn't a machine in the office that is always on.
I'm looking for options on scanning to Windows / Mac devices from a C400. I'm reluctant to use the email scanning as the documents are sensitive and I don't know how the email would route.
The organisation uses Office365 - I'm not sure if there is any integration with it?
Am I best just installing the drivers on the desktops/laptops and using scanning software or is there a better option?