Use this parameter to remove the Send On Behalf Of permission to the mailbox specified by the Identity parameter from the ...

Use this parameter to remove the Send On Behalf Of  permission to the mailbox specified by the Identity parameter from the user specified by the trusted user parameter. This parameter accepts the arguments True or False. These arguments are not case sensitive. When using a CSV file, specify RemoveSendOnBehalfOf True to remove the permission or RemoveSendOnBehalfOf False to not remove the permission. Specifying False will not add the permission if it is already set. To add the permission, use Add-MSOnlineMailPermission.