CTS Advisory: Issues with Apple Mail on iOS 11
Due 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.
How can you 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, if you are experiencing this issue, Microsoft recommends that you download the free Outlook for iOS app available from the App Store. Alternatively, you can avoid updating to iOS until the issue has been fixed.
More information can be found here: https://support.microsoft.com/en-us/help/4043473/you-can-t-send-or-reply-from-outlook-com-office-365-or-exchange-2016-i
If you have any questions, please contact the CTS Help Desk at 412.396.4357 or email@example.com