Any EU (including the UK) organisation using US cloud services (Microsoft 365, Google Apps, Amazon Web Services, Rackspace Hosting etc.) will have to find alternatives before GDPR kicks in next May.
https://kopano.com/kopano-documents/EU-US-Cloud-Privacy.pdf
https://www.youtube.com/watch?v=BiUYWIqsQ9Y&feature=youtu.be
The alternative is Igaware: www.igaware.com