Apple has announced that iOS 11 will be released to the public on Tuesday, September 19th.

Normally, this is a wonderful occasion because companies such as Apple provide fixes and features that make our lives better! Unfortunatly, iOS 11 is going to introduce issues for a lot of customers running Windows Server 2016.

We have been testing the BETA releases of iOS 11 for a couple of months and are working with Microsoft and Apple to resolve the issue but, unfortunately, the issue still exists with the Golden Master (GM) release of iOS 11.

The high-level overview of the issue is that Exchange ActiveSync (EAS) users will not be able to REPLY to, or FORWARD, messages with attachments from the default Mail app on iOS 11. Please understand that this is NOT a SmarterMail issue but an iOS 11 and Windows Server 2016 compatibility issue that affects ALL versions of SmarterMail as well as other mail servers and services, including Microsoft Exchange Server customers using Windows Server 2016.

If you are using Windows Server 2016, please read further for a more detailed explanation and workaround:

The cause of the issue is related to the implementation of HTTP/2 in either Windows Server 2016 or in iOS 11. HTTP/2 is a major revision of the HTTP network protocol used for communication across the internet. Windows Server 2016 and Windows 10 both implement, and default to, HTTP/2 versus the more legacy HTTP/1.1. With iOS 11, Apple is now using HTTP/2 because Windows Server 2016 supports it.

If your mail server is running and older version of Windows Server, you will not see this problem as iOS 11 will continue to use HTTP/1.1.

As a workaround, system administrators can modify the Windows Server 2016 registry to “act as” previous versions of Windows Server, essentially telling iOS 11 to use the HTTP/1.1 protocol. The following keys would need to be modified AND the server rebooted:

Again, this is ONLY necessary if your mail server is running Windows Server 2016. NOTE: Editing the registry should be handled by someone with experience. If you aren’t comfortable with making registry changes , open a ticket with our support team.

We are going to continue reaching out to Microsoft and Apple to help them resolve the issue. We will update our customers when we have more information.

We hope this information helps you continue to provide seamless mail services for your customers.

Thank you for using SmarterTools products!
The SmarterTools Team