#Exchange #Exchange2010 .. stumbled on this. We are using F5 LTM’s to front our Cas Arrays .. the workaround is really rubbish!
Intermittent mail delivery issues are experienced on BlackBerry smartphones when Microsoft Exchange is configured behind a load balancing appliance
Users receive a red X when sending new email or replying to emails from their BlackBerry smartphones in what appears to be a random pattern. If an affected user sends the message again, it is delivered.
In environments that incorporate hardware or software load balancing appliances, such as Big-IP, Barracuda, or F5, issues can be encountered in which sporadic error messages regarding reaching users’ mailboxes or performing basic communication functions appear in both Windows Event Viewer and the BlackBerry Messaging Agent (MAGT) debug logs. These error messages are typically repetitive and occur approximately every 5 to 7 minutes once the initial issue is encountered.
… Workaround .. Bypass the hardware load balancer with a hosts file entry so that the BlackBerry Enterprise Server may communicate directly with a single Client Access Server.