Turning off/turning on didn't help.
It's a five month old iPhone 6.
The Mail function was working when I left it on a table for an hour but the screen was reconfigured when I next picked it up.
Power was down to 3% and there was a brief message about a low power mode when I plugged in the recharger.
Rebooting at 100% has had no effect.
(30 minutes later)
Just installed an update and asked Siri to "find mail".
Result was that Mail is not installed and needs to be downloaded from App Store.
Several unsuccessful attempts later I am contemplating going Android.
Didn't have any problems with my last two iPhones but this one is looking like a lemon.
My music library vanished a couple of weeks after I got it, it has sporadic Bluetooth connection problems in the car and now this.
