I'm battling against this darn issue this morning. We have the following setup:

Big Hyper-V machine hosting the servers as VM's

VM for CAS: WEB.XXX.local VM for Mailbox: EXC.XXX.local

Servers are running Server 2008 R2 with Exchange 2010 SP1 Clients are all running Windows 7 Pro x64 with Outlook 2010 x64

The problem we're having is that nobody is able to see any emails received today (16th of October), but they are able to send externally. When I reply back to the email received externally, I don't get an NDR, yet the user cannot see my email.

This is what I found and tried thus far:

• If we create a subfolder in Outlook 2010 and move any email from the inbox into that folder, changes will be immediately reflected in OWA
• We've been sending test emails to other users internaly and external email addresses and the sent items folder contains all those tests, synced properly to OWA as well
• Have tried crating a new profile, new emails are still missing
• Tried disabling Cache Mode, still no luck
• Also disabled "Download shared folders", still no luck
• Tried to setup a brand new Exchange mailbox and configured it on a VM that never had Outlook on it, still the same issue
• Tried restarting Exchange services on both CAS and Mailbox servers, no luck
• Tried rebooting both CAS and Mailbox servers, still no luck
• Performed a Mailbox Discovery on my admin account, emails from today are being found in the Discovery results, so the stuff is there, just not updating the user inboxes

Any idea about what this hellish thing can be? I've done everything I can think of and also everything I could find out there.

Let me know if you need any more details and thanks for reading this!