The is a lot of blogs saying weird things on this particular Powershell command.

Here the right one.

$onrepm = get-credential

'alias for the user' | New-MoveRequest -OutBound -RemoteTargetDatabase 'local database' -RemoteHostName 'ewsurl' -RemoteCredential $onprem -TargetDeliveryDomain 'localsmtpdomain'

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