Apple's TestFlight program now allows developers to send out emails via the iTunes Connect app to up to 1,000 beta testers. TestFlight allows developers to test their apps before releasing them to the App Store with up to 25 internal members of the team and 1,000 external testers through an email invite.
You can now invite up to 1,000 testers to beta test your iOS apps by simply sending them an email invitation through iTunes Connect. Once they accept your invitation, testers can install your beta app on their iOS devices, get updated builds, and provide feedback, all within the TestFlight app.
If you're a developer curious about TestFlight, be sure to check out our exploration of the app and service.
Source: Apple Developers