If you are using the native mail app on your iPhone or iPad, and upgrade to iOS 11, you may encounter issues.
Do to an incompatibility in the new release of iOS, users of the built-in Apple Mail app in iOS 11 may be unable to sync their Office 365 mailbox or login to their accounts. iOS 9 or 10 users are not affected.
What do I need to do to fix this?
Microsoft and Apple are working to resolve this issue and will post more information to the article, below, when it becomes available.
In the meantime, we recommend you download the free Outlook for iOS client, available in the App Store.
Alternatively, you can avoid updating to iOS 11 until the issue has been fixed. Please click Additional Information to learn more.