How do I suppress Yes/No Prompt when Saving digitally signed Mail in a format that is not secure?

I wrote VBA to save an email as a text file.

For digitally signed emails it prompts me if I want to save the file in a format that is not secure (yes or no to continue). I want to suppress this warning.

I tried the following:

With Application
     .EnableEvents = False
     .ScreenUpdating = False
End With
Application.DisplayAlerts = False
m.SaveAs savePath, olTXT 
With Application
     .EnableEvents = True
     .ScreenUpdating = ture
End With

And

Application.DisplayAlerts = False
m.SaveAs savePath, olTXT 
Application.DisplayAlerts = True

They both do not work (I get a compile error). How do I turn off these alerts in Outlook?