iMessage is the messaging service built into Apple's operating systems for iPhone, iPad, Mac, Apple Watch and Apple Vision Pro. It lets users send text messages, photos, videos and files to other Apple devices within the Messages app. According to Apple's Platform Security guide, iMessage relies on the Apple Push Notification service for delivery, and message content and attachments are protected with end-to-end encryption, so that only the sender and the recipient can read them. The software is proprietary.
Apple Inc. is a US company. Because the provider is established in the United States, it is subject to US legal process, including the CLOUD Act, regardless of where its servers are located. Apple's guide says that it does not store message content or attachments and cannot decrypt them. However, the guide does not state where the identity and routing data used by iMessage are processed. A European organisation that needs to keep communications within the EU should weigh this against its own requirements and consider a messenger with EU-operated infrastructure and published hosting terms.