In This Exchange Server 2016 article I will show you how to locate your mail Queue database and check that Is working OK.
The location of the mail queue on Exchange Server 2016 Is:
C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\data\Queue
The name of the mail queue database Is mail.que
To get more details about the Queue type:
Get-Queue | fl
In my last Exchange article I showed you how I installed all prerequisite using PowerShell.