Outlook 2010 SP1 RU3, Windows Server 2008 R2.
Two mailbox servers, EX001 and EX002, each hosting one Database, DB01 and DB02, in a DAG, DAG01. Two HT/CAS servers with NLB, hosting the CAS Array.
Seeming random users are unable to log into their mailbox on DB01 using Outlook. Get a dialogue stating:
"Cannot open your default e-mail folders. Microsoft Exchange is not available. Either there are network problems or the Exchange server is down for maintenance."
OWA works fine.
Other users on DB01 are able to login just fine. Moving the problem users to DB02 allows them to login via Outlook.
Outlook is configured using the name of the CAS Array, and tests successfully.
Any new profile setup, or existing one, fails. This started happening about a week ago. No maintenance was performed on these systems in that time frame. Prior, mail was working.
Any thoughts? We are seeing incidents of EventID 9646, but they appear to be unrelated. We are looking at increasing the Maximum number of sessions to resolve this, however.
Thanks!