Epic Games CEO Tim Sweeney was asking Apple to open its phones to other app stores as early as 2015, according to new emails made public as part of the companies’ antitrust trial. Under the subject line “iOS as an open platform,” Sweeney emailed Apple CEO Tim Cook directly to make the case for allowing other app stores to distribute software on iOS.

“The App Store has done much good for the industry,” Sweeney wrote to Cook, “but it doesn’t seem tenable for Apple to be the sole arbiter of expression and commerce over an app platform approaching a billion users.”

In particular, Sweeney asked to “separate iOS App Store curation from compliance review and app distribution,” essentially suggesting that Apple could maintain its security features across the platform without routing all downloads through the central App Store.

It’s a powerful distinction for the ongoing trial, in which Apple is arguing that App Store exclusivity is necessary to maintain the existing security and privacy features on iOS. These are part of the compliance process referenced by Sweeney in the email, and other ecosystems have been successful in implementing them across multiple app stores. Most recently, Google introduced a similar system on Android under the name Play Protect, guarding against malicious downloads even from side-loaded software.

Cook responded by forwarding the message to Phil Schiller with a question: “Is this the guy that was at one of our rehearsals?”

It’s likely that he was: a few weeks earlier, Epic Games had made an appearance at Apple’s WWDC event, touting the company’s work using Apple’s Metal API, although Sweeney did not appear onstage.

Other emails show Sweeney continuing to push Apple behind the scenes, asking Epic co-founder Mark Rein to push for a meeting with Greg Joswiak in January 2018. “If the App Store [were] merely the premier way for consumers to install software and not the sole way, then Apple could curate higher quality software overall, without acting as a censor on free expression,” Sweeney argued.

Rein was ultimately able to arrange a hearing for the idea through Apple’s Tim Kirby and expressed enthusiasm. “He was definitely receptive to the idea,” Rein wrote, “which doesn’t mean it will go anywhere, but does mean he’ll line up people who will listen and not shoot it down like Phil Schiller would…. so maybe there’s a smallest little crack on the very outer surface of the many feet of ice covering the frozen lake that is the Apple store.”

Six years later, the ice has yet to thaw.