Just because it’s new doesn’t mean you need it. While iOS11 has some amazing new features, there’s a significant problem with Outlook.com, Office 365 and Exchange mail accounts. Apple and Microsoft have both acknowledged that mail fails to send in some cases with iOS11. Both are reportedly working together to get the issue resolved.
For those of you who don’t use Microsoft for mail services, we can recommend upgrading to iOS11. Keep an eye out for subsequent updates, where issues, like the one above, are patched.
UPDATE: iOS 11.0.1 has been released today. This update is designed to resolve the issue sending mail from an iOS device hosted with Microsoft Exchange, Outlook.com and Office 365. You can follow this tutorial to update your phone to the latest version.