Apple has confirmed that it is working closely with Microsoft to resolve an issue with Mail syncing in iOS 11.
Some users have discovered that they are unable to send emails using their Exchange or Outlook accounts since updating their devices. Apple promises a fix will be available in a future iOS 11 release.
iOS 11 is a huge upgrade that brings a whole bunch of big improvements and new features. Most iPhone and iPad users will have been scrambling to get their hands on it as soon as it rolled out to the public on Tuesday. Sadly, some are paying the price for updating early.
Apple has acknowledged an issue that prevents some users from sending email from an account hosted by Microsoft on Outlook.com or Office 365, or an Exchange Server 2016 running on Windows Server 2016.
“Cannot Send Mail. The message was rejected by the server,” reads the error message that is received.
In a new support document, Apple says it is “working closely with Microsoft to resolve the issue” and will implement a fix “soon” in another software update.
The only workaround for now, as far as we can tell, is to send the email from another device, or an earlier version of iOS.