We reported a few days ago that after Apple started rolling out iOS 11 some users were having issues with their Outlook.com and Office 365 email accounts.
Users with an Outlook.com, Office 365, or Exchange 2016 email account were not able to send emails using the default Mail app in iOS 11. When trying to send a mail, users will hit the “Cannot Send Mail. The message was rejected by the server.” error. A fix for the issue was not available, but Microsoft is recommended users to install the Outlook app for iOS as a workaround. In addition to that, users using Exchange 2016 could workaround the issue by temporarily disabling HTTP/2 in Windows Server 2016.
Apple said they were working closely with Microsoft to resolve the issue and the company has now released an update to iOS 11, taking it to version 11.01.
The update fixes the issue and the Apple support documentation notes:
“You might not be able to send email with an Outlook.com, Office 365, or Exchange account until you update to iOS 11.0.1.”
Affected users can wait for the update to be pushed out or can install it immediately by going to Settings > General > Software Update.