Frenemies Box and Microsoft team up again.

By Barb Darrow
June 27, 2017

It doesn’t look like Box has ever met a cloud provider it doesn’t like. On Tuesday, the company, which sells cloud-based file storage and synchronization services to businesses, named Microsoft Azure as a “strategic cloud platform.”

In this case, that means Box box and Microsoft msft will both sell “Box on Azure” to business customers around the world, according to a Box spokeswoman. She added that this is the first time Box is “going to market” with one of the big four public cloud providers. That may be, but it certainly has cozied up to all of them.

Microsoft Azure is known as a public cloud—a huge aggregation of servers, storage, and networking—owned and operated by Microsoft at data centers worldwide. It sells those resources to many customers. Azure competes with Amazon amzn Web Services, Google googl Cloud Platform, and IBM ibm SoftLayer in this booming market, driven by many businesses that don’t want to invest more in their own data centers

Related: Welcome to the Era of Data Center Consolidation

Box started out 12 years in the pre-cloud era and so fielded its own data centers. In the intervening years, it’s partnered with AWS and other cloud providers in many ways. Box CEO Aaron Levie once told Fortune that if Box had started later, it would have stayed out of the data center business altogether.

Two years ago, Box launched a partnership with IBM under which it uses IBM cloud data centers in some regions where customer data must remain in the country of origin. It subsequently announced a similar deal with AWS to use that cloud’s facilities in Canada and Australia.

Related: Box CEO Says Security Concerns Drive Big Companies

Box also works with Google, generally seen as the third largest cloud provider after AWS and Microsoft, to integrate box storage with Google Apps.

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Under terms of this latest Microsoft collaboration, Microsoft and Box sales teams will get credit for selling Box on Azure—a key motivator for salespeople who must make quotas. Box will also make use of Azure’s artificial intelligence (AI) and machine learning perks, the Box spokeswoman said. Box will also “explore ways” to integrate with Azure’s computing capabilities.

Box already works with Microsoft to integrate Box storage with Microsoft Office 365 applications. And, for the record, Microsoft OneDrive cloud storage competes with Box storage. So this is a complicated world with companies partnering in some arenas and competing in others.

Microsoft, like Amazon and IBM, has been wooing third-party Internet software providers—companies like Salesforce crm , Tableau data , Workday wday , and yes, Box—to run their respective public cloud data centers. The competition is fierce.

Last year, when asked by Fortune whether it is hard for a company like Box to rely on big cloud providers that also compete with his company, he replied: “You know what’s harder? Building data centers!”

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