iOS 6.1 devices are hammering Exchange servers with excessive traffic, causing performance slowdowns that led Microsoft to suggest a drastic fix for the most severe cases: throttle traffic from iOS 6.1 users or block them completely.
"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," Microsoft wrote on Tuesday in a support document.
The problem also affects Exchange Online in Microsoft's Office 365 cloud service. Office 365 customers may get an error message on iOS 6.1 devices stating "Cannot Get Mail: The connection to the server failed." The Microsoft support article says both Apple and Microsoft are investigating the problem.