CmdID / PowerShell / Cmdlets / Remove
Remove-AdfsDeviceRegistrationUpnSuffix
Removes a custom UPN suffix. Windows Server PowerShell reference
From the Windows Server PowerShell reference 4 parameters Its page in the reference
Parameters
-ForceForces the command to run without asking for user confirmation.-UpnSuffixSpecifies a UPN suffix.-Confirm, -cfPrompts you for confirmation before running the cmdlet.-WhatIf, -wiShows what would happen if the cmdlet runs.