Apple is sending out emails to a small selection of iCloud customers informing them of a specific bug in iOS 10.3. The bug it appears that evidently reasons some iCloud services that have been in the past disabled to be re-enabled.
From the e-mail, got via MacRumors:
We found out a bug in the hot iOS 10.3 tool update that impacted a small selection of iCloud customers. This may have inadvertently reenabled some iCloud services that you simply had in the past disabled in your software.
We advise you move to iCloud settings for your iOS software to ensure that most effective the services you need to make use of are enabled. Be informed extra about find out how to arrange your iCloud settings or touch AppleCare with any questions.
Out of doors of "small", it is unknown presently what number of iCloud customers this may have impacted.
You'll be able to test which iCloud services are enabled for your iPhone or iPad with iOS 10.3 by way of heading to Settings, then tapping the Apple ID banner on the most sensible of the Settings web page and tapping iCloud.