There is nothing contentious about the macro. It should not cause errors if entered as shown. The only line that needs to be changed is

.To = "someone@somewhere.com", where you need to replace the address with an actual address (though this dummy address should not cause an error).

Select a message and use the following macro to test the code and highlight where the error occurs.

Sub Test()
Dim olMsg As MailItem
    On Error Resume Next
    Set olMsg = ActiveExplorer.Selection.Item(1)
    SendOnMessage olMsg
lbl_Exit:
    Set olMsg = Nothing
    Exit Sub
End Sub