Since the release of iOS6, several issues have been identified with this version when used in conjunction with Exchange:

• Meeting Request where the device user becomes the meeting organizer, which can potentially enable attendees to cancel the meeting for everyone invited. This issue has been documented in KB2768774;
• Autodiscover not working properly when the e-mail address doesn’t match the user’s UPN.

The Exchange Team published an article where they mentioned several suggestion to “mitigate” the issue; mitigate is quoted here, because some of the suggestions mentioned are in my opinion non-options in a corporate environment, like the suggestion to switch to IMAP/POP. Not only does that remove calendaring functionality, it’s also a lot of work and hassle for end users for the – I expect – short period before we see an iOS update from Apple, after which people can go back to using Exchange ActiveSync again.

How to deal with this issue in the – relatively short – period between now and the iOS 6 fix, depends on the risk your organization is willing to take. When you’re not willing to take any chances, you can block IOS 6 devices using Exchange’s Allow/Block/Quarantine (ABQ) feature or blocking them on the Reverse Proxy level, e.g. ISA or TMG; more information on how to accomplish the latter here. While being a rather draconic measure, it might prove a better temporary measure when compared to the suggestion to ask end users not to take action on calendars in iOS, which could be an accident waiting to happen.

As a more user friendly solution, I’ll gladly bring to your attention a script created by UC Architects fellow Steve Goodman, which can collect information on current iOS users in your environment. Then, with this information, you can selectively pick out iOS 6 devices and communicate the issues with their users until a fix is released. You can get the script here.

Note that there are reports of Apple currently testing IOS 6.0.1 and it is rumored the Meeting Request fix will be included.

Update, November 1st, 2012: Apple released IOS 6.0.1 which fixes the meeting request issue amongst other things (but not the Autodiscover issue). Update your IOS device Over The Air or using iTunes.