I was recently found myself with a couple of calls from Tier 1 Support Team that random Users were unable to use MS Outlook.
I followed standard procedure and asked for a “Clear definition of the problem”, the response was: “The connection to Microsoft exchange is unavailable. Outlook must be online or connected to complete this action”
I quickly connected to one of the workstations of the affected user and did some basic troubleshooting:
1. Went to Control Panel and created a new Mail Profile
and BAM!, the automatic discovery did not kick in as it always does, and it was prompting for credentials.
2. Input the credentials DOMAIN\%USERNAME% and the password, clicked on Save password and it started to connect
and BAM!, the user is not found.
3. I modify the Microsoft Exchange Server name to my secondary Exchange CAS Server, click on check name and it finds the user and changes the Server backup to EXCHANGE-CAS.DOMAIN.COM
4. I think to myself, I’m in the clear it went through, but why didn’t Auto discovery work, and why do I have to manually workaround it? E-mails begin to download everything seems good and then BAM! Address Book throws error: “The connection to Microsoft exchange is unavailable. Outlook must be online or connected to complete this action” .
I asses the situation:
1. Random users (from Site 1) have issues connecting to the primary CAS Server
2. Random users (from Site 2) have issues connecting to the primary CAS Server
3. Checked Outlook connectivity, everything is OK
4. Event Logs on primary CAS and affected workstations, No errors
5. I go to Primary CAS Server to Exchange Management Shell and verify which database is using what CAS server: Get-MailboxDatabase |select name, RpcClientAccessServer
6. Using command Set-MailboxDatabase -identity <databasename> -RpcClientAccessServer <CASServerName>, and I assign another CAS to the database where the random users are experiencing issues.
7. I call Tier 1 Support Team and ask them to have the users close and reopen MS Outlook.
8. Issue was resolved.
9. I then checked the primary CAS did a thorough check, fixed some issues on it rebooted and it was working perfectly again .
