Once again, Google is pressuring Apple to open up iMessage -- and this time, it's doing so by way of a letter to European regulators. Joined by CEOs from major European telecommunications companies, an unnamed Google senior vice president signed a letter saying that Apple's iMessage should be regulated as a core platform service under the EU's new Digital Markets Act (DMA). 

The DMA keeps an eye on companies providing services that are widely used and are considered vital to the digital economy. One of the DMA's purposes is to foster fair competition and prevent tech giants from abusing their market power. 

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These core platform services include social networking sites, search engines, operating systems, cloud computing, advertising, and messaging services. 

The letter -- signed by tech leaders from Google, Orange, Vodafone, Telefonica, and Deutsche Telekom -- makes the case that Apple's iMessage meets the DMA criteria for core platform services, being used by at least 10,000 active users monthly in the EU and operated by a company with annual revenues above