Microsoft is going to start selling Box’s content services to customers of its cloud platform as part of a new deal the two companies announced today. Both businesses will start pushing a “Box on Azure” offering that will allow enterprises to use the content services platform while storing files in Microsoft’s cloud.

As part of the deal, Azure will be used for expanding the Box Zones service, which also uses data centers from Amazon Web Services and IBM to let companies store data in particular countries. Box also plans to integrate Azure’s machine learning services with its offering in order to provide intelligence to customers. In addition, the company is looking to integrate its Platform services for developers with Azure’s compute infrastructure.

It’s an interesting move for Box, considering that Microsoft operates a competing OneDrive for Business service. The two companies have been frenemies for a while, and in many cases Box customers also use Microsoft’s other tools, so promoting both would seem a sensible approach.

“At Box, we’ve architected Box as a multi-cloud platform and our goal is to ensure our customers can take advantage of the best the cloud has to offer, from a variety of platforms, and that we integrate with all of the apps and services our customers use,” a company spokesperson said via email. “This announcement with Microsoft is just the beginning of our partnership, and we will continue to build out more joint offerings over time.”

One of the key unresolved parts of this partnership is what happens to Box’s KeySafe encryption offering, which lets enterprises bring their own encryption keys to the content services platform. KeySafe is one of Box’s most popular services and currently relies on Amazon Web Services to provide the key management functionality. The company said that it doesn’t have anything to announce around a version for KeySafe that works with Azure, so it’s unclear if or when customers would be able to use the same services with Microsoft’s cloud.

Box will continue to operate existing services that run on Amazon Web Services’ infrastructure following the deal. The company has made it clear that its service is designed to run in a multi-cloud configuration, so it makes sense for it to continue operating its services with Microsoft’s biggest competitor.

At the same time, this deal seems deeper than the work Box has done with AWS in order to provide its existing KeySafe and Zones functionality, so this Azure partnership will be an interesting one to follow.