iPads and iPhones running the newest version of iOS are being blocked in some enterprises because bugs are overloading corporate Exchange servers
One of the benefits of Apple's iOS devices such as the iPad and iPhone is that you can upgrade to the latest version as soon as it comes out. Being on the cutting edge is usually a good thing, but sometimes it can come back to bite you. If you are connecting to an Exchange server for mail and calendar services, the latest version of iOS has an unpleasant surprise in store for you.
Reports started surfacing in late January about excessive logging on Exchange servers caused by the upgrade to 6.1. A report on Microsoft Technet states:
I had a user upgrade to 6.1 and immediately after he finished, his phone/IPAD started causing excessive logging on the exchange server.
I found the problem by using exmon and saw the CPU utilization in conjunction with high session count.
He shut down Outlook and the problem remained. He turned off his iPad and the problem went away. The only change he said he made that morning was upgrading to iOS 6.1.
--> Please see the rest on the website, I did not have many customer returns yet : http://www.zdnet.com/ios-6-1-banned-from-corporate-servers-due-to-exchange-snafu-7000011064/