Microsoft has issued a bug report to inform that iOS 6.1 devices may slow down Exchange servers, recommending server administrators to either block or create a custom throttling policy for iOS 6.1 users.
According to the advisory, “when a user syncs a mailbox by using an iOS 6.1-based device, Microsoft Exchange Server 2010 Client Access server (CAS) and Mailbox (MBX) server resources are consumed, log growth becomes excessive, memory and CPU use may increase significantly, and server performance is affected.”
At this point, the only way to fix the issue is a new software update, but Microsoft has posted three different workarounds that could help administrators keep their Exchange servers alive and running.
First of all, they could remove and re-create the device partnership, but in case this fails to do the job, administrators should create a custom throttling policy for iOS 6.1 users. If that doesn’t work, the only way to deal with the issue is to completely block iOS 6.1 users.
You can find more information on the bug, plus additional details on these workarounds, on this page.