Open PowerShell with the Exchange PowerShell CMD Tool Check the Health of Exchange: Test-ServiceHealth Check the Exchange Database Status: Get-MailboxDatabase -Status | Format-List name,server,mounted Check the Queues: Get-Queue | Select Identity,Status,MessageCount Open up Event Viewer and Read the logs and check what's going on. If you cannot start the EdgeSync Service. Re-Add: New-EdgeSyncServiceConfig - Site YourSitesandServicesLocation Start --> Run --> services.msc Re-Start the services. If Microsoft Filtering is hung. Bounce the server. Mail should start flowing again. If not...Microsoft Support is your friend. Don't take all day...troubleshoot what you can and then bow humbly, give up and call support. Your busy right? Microsoft US Support: 1 ( 800) 642-7676 Microsoft US Support (URL): https://support.microsoft.com/en-us/assistedsupportproducts Mount Exchange Database Mount-Database -identity Domain\Exchange Server Name\ mailbox name Get