That was fast. Apple has released iOS 11.0.1, an update to iOS 11 for iPhones and iPads that fixes a bug that meant some users were unable to send mail to Office 365 and Exchange.
Articles describing the bug were updated on Apple and Microsoft websites Tuesday. Previously, iOS 11 users experiencing the problem would see the error message "Cannot Send Mail. The message was rejected by the server," when attempting to connect to Office 365 or certain versions of Exchange server. (See Whoops! Apple's New iPhone Software Breaks Office 365.)
iOS 11, which shipped this month, is particularly focused on beefing up the iPad as a tool for business, with new multitasking features and a Files app to make it easier to access information located on iCloud and other cloud storage services, including Box and Dropbox. Previously, Cisco, SAP and IBM have partnered with Apple on making iPhones and iPads good citizens on their enterprise estates. (See Apple's Cloud Strategy Will Save the iPad and Apple Launches Animated Poop Emoji, iPhone X.)