We have an odd error with a few mailboxes on our exchange 2010 sp3 server, there are various reports of similar issues and we have ruled out the following:
*windows firewall is not enabled
*CRM is not used
*Outlook is using cached exchange mode
*DNS is not using IPv6 address
*Same issues occur with AV disabled
*Inherited permisions are enabled
*Nothing of note in the event logs
*Exmon doesn't show high usage by one user
*active sync ping collision is present in active sync logs but doesn't seem related?
*same issue happens on ios and windows phones so would seem to be effecting all devices
*have resynced all devices
Any one get any more ideas or things to try?