Open Outlook and press ALT+F11 to open VBA. Add the following code to "ThisOutlookSession" or create a new "Module" with the right mouse button.

You can set the email address at the bottom of the code.

 Dim WithEvents objInspectors As Outlook.Inspectors
Dim WithEvents objMailItem As Outlook.MailItem
Dim WithEvents myOlExp As Outlook.Explorer

Private Sub Application_Startup()
    Initialize_handler
End Sub

Public Sub Initialize_handler()
    Set objInspectors = Application.Inspectors
    Set myOlExp = Application.ActiveExplorer
End Sub

Private Sub objInspectors_NewInspector(ByVal Inspector As Inspector)
    If Inspector.CurrentItem.Class = olMail Then
        Set objMailItem = Inspector.CurrentItem
        If objMailItem.Sent = False Then
            Call SetFromAddress(objMailItem)
        End If
    End If
End Sub

Reply
Private Sub myOlExp_InlineResponse(ByVal objItem As Object)
    Call SetFromAddress(objItem)
End Sub

Public Sub SetFromAddress(oMail As Outlook.MailItem)
    oMail.SentOnBehalfOfName = "username@domain.com"
End Sub