Outlook 2003 Service Pack 3 Clients
During normal working hours users randomly was unable to access their mailboxes when they launched their Outlook client.
“Unable to open your default e-mail folders. The Microsoft Exchange Server computer is not available. Either there are network problems or the Microsoft Exchange Server computer is down for maintenance.”
It was also reported that some users had issues expanding additional mailboxes. (Delegate Mailboxes )
The following Outlook message appeared.
Or users have issues opening Shared Calendars.
With Get-ThrottlingPolicy you can see the value of RCAMaxConcurrency
I changed RCAMaxConcurrency to 214748364 and the problem is fixt:
Get-ThrottlingPolicy | set-ThrottlingPolicy -RCAMaxConcurrency 214748364