5/30 Update: Exchange 2010 SP3 RU1 is out, which also fixes this issue.

2/19 Update: iOS 6.1.2 is out: https://blog.jasonsherry.net/2013/02/19/ios-6-1-2-is-out/. Here’s the text of the update message:

Fixes and Exchange calendar bug that could results in increased network activity and reduced battery life.

http://support.apple.com/kb/DL1639

2/16 Update: Per several blogs 6.1.2 should be coming out 2/20 and will fix this Exchange bug, in addition to a lock screen security issue and other items. Bit more info here: http://www.redmondpie.com/ios-6.1.2-releasing-early-next-week-to-fix-exchange-and-lock-screen-passcode-bugs/

2/13 Update: Apple’s KB on this issue: http://support.apple.com/kb/TS4532
It just says to turn Calendar syncing off and back on currently.

2/12 Update: Offical MS KB now out : KB2814847
Rapid growth in transaction logs, CPU use, and memory consumption in Exchange Server 2010 when a user syncs a mailbox by using an iOS 6.1-based device

This KB  includes a notes for Office 365 users on what they may see on their device when blocked. Office 365 and Exchange 2010+ both include client throttling code, misbehaving Office 365 clients are blocked or throttled much more quickly than Exchange 2010/2013 clients. This KB includes instructions on how to setup throttling policies and find misbehaving iOS clients.

2/11 Update #2: Tony Redmond now has a more detailed post on this issue here now: http://thoughtsofanidlemind.wordpress.com/2013/02/11/ios6-activesync/.

Apple has released 6.1.1, for iPhone 4S only currently, but it looks like this was rushed out mainlyto fix some cellar/3G communication issues . So it may not fix the code that is causing the logging issue on Exchange.

Paul Cunningham also created this post today: How to Block iOS 6.1 ActiveSync Devices from Exchange Server 2010. However, this could be a career limiting move if you block your CxOs and VIPs.

2/11 Update: I’ve also heard that deleting the ActiveSync partnership will cause the device to stop retyring the bad calendar command. This will be a better method, politically, than blocking all iOS 6.1.

Orginal 2/10 post:
I’ve heard this from several sources and now it’s on ZDNet: http://www.zdnet.com/ios-6-1-banned-from-corporate-servers-due-to-exchange-snafu-7000011064/. This ZDNet article refers to this TechNet forums post: http://social.technet.microsoft.com/Forums/en-US/exchangesvradminlegacy/thread/d7f4b534-2eac-4291-9564-97a9875056ee.

Tony Redmon has also covered it here: http://www.windowsitpro.com/blog/tony-redmonds-exchange-unwashed-50/exchange-server/apple-ios-61-upgrade-excessive-transaction-log-growth-145223

Per feedback, I haven’t seen this issue 1st hand yet, this is due to iOS sending an incorrectly formatted response to a meeting invite or update. Exchange returns an error and the iOS devices keeps retrying the request, over and over again. This in turn generates IIS and transaction logs on the Exchange servers.

This is yet another issue in the long list of poorly written iOS code issues in relation to Exchange. As of 2/10/13 this issue hasn’t made the official list of 3^rd party device ActiveSync issues

KB256324: Current issues with Microsoft Exchange ActiveSync and third-party devices
KB2768774: Meeting in Attendee’s Calendar Loses Track of the Meeting Organizer. This KB also list several fixes included in iOS6.

Here’s a previous blog post on iOS 6.0 issue: https://blog.jasonsherry.net/2012/10/16/another-iphone-ios6-0-issue-with-exchange/

If you think you might be experiencing this issue use Exchange Server User Monitor to identify users causing an excessive load on your Exchange server. You can then block\quarantine the user(s) device or use ActiveSync policies to block all iOS 6.1 devices. See this EHLO blog post on how to do this: Controlling Exchange ActiveSync device access using the Allow/Block/Quarantine list

Or you can tell your users to not respond to meeting invites or updates from their iOS devices and trust them to do this (yeah right…).