The iPhone maker said in a statement it “took steps to protect our users by blocking techniques that exploit fake credentials in order to gain access to iMessage.” It added that “these techniques posed significant risks to user security and privacy, including the potential for metadata exposure and enabling unwanted messages, spam, and phishing attacks.”

The company said it would continue to make changes in the future to protect its users. The announcement comes a day after Beeper Mini, the latest app to enable iMessage on Android devices, stopped working. Apple’s iMessage offers encrypted messaging between iPhones, Macs, iPads and other devices made by the company, and it has resisted calls for nearly a decade to expand the service to Android.

Some users have long argued that the lack of an iMessage app for Android makes messaging between the two platforms less secure. Apple recently said it would support RCS, or rich communication services, later next year. That’s a replacement for the standard SMS service that will enable an improved texting experience between platforms.

Read more: Apple to Adopt Texting Standard That Works With Android

Beeper was founded by Eric Migicovsky, who is known for creating the Pebble smartwatch in the years before the Apple Watch and for being part of Y Combinator, the tech industry’s most prestigious business incubator.

In an interview, Migicovsky said his new company continues to work on Beeper Mini and is “feeling good” about again bypassing Apple’s restrictions. He said that Beeper Cloud — a variant of Beeper Mini — is still working. Beeper Mini, he says, is more secure and connects directly to Apple services, while Beeper Cloud uses third-party servers.

“The passion and energy people had this week is indicative of the importance of what we’re doing,” Migicovsky said. He denied that Beeper Mini creates security issues for users, saying his app enables encrypted messaging between Android and iOS so less security is a false notion.

Migicovsky, who said he hasn’t heard from Apple about his service, was selling Beeper Mini for a $1.99 per month subscription after a one week free trial. Apple doesn’t charge a subscription to use iMessage on its devices.

Apple said it can’t verify that messages sent through unauthorized systems that masquerade the use of Apple credentials are actually end-to-end encrypted. Other services, including one called Sunbird, have previously tried to make iMessage work on Android. Those efforts were also shuttered by Apple.

Despite adding support for RCS next year, Apple executives have publicly and privately shot down the idea of making it easier for iOS and Android users to communicate. Last year, Apple chief executive officer Tim Cook suggested that a user who wanted to more easily message with his mother on Android buy her an iPhone.

Craig Federighi, Apple’s software engineering chief, said in an email to fellow executives several years ago that “iMessage on Android would simply serve to remove an obstacle to iPhone families giving their kids Android phones.”

The company’s operating systems will further open up next year in the European Union with the Digital Markets Act, which will require Apple to allow third-party app stores in the region.