Apple's new operating system won't work on older models of the iPhone and iPad and is causing problems for some people using the Mail app.
iOS 11 was released overnight in New Zealand and comes with a suite of new functionality and design features.
iOS 11 will be available on the trio of new iPhones released last week and be compatible with the following models of iPhone, iPad and iPod:
iPhone: 5s, 6, 6 Plus, 6s, 6s Plus, SE, 7, 7 Plus, 8, 8 Plus, X
iPad: 5th generation (2017); Mini 2, 3 and 4; all Air models and all Pro Models