Remove Add... button from Send Mail

We would like to removed the "Add..." button from the Send Mail dialog.

This button is under the attachments section.

This Send Mail page is launched from the Collaboration Launch Pad.

How can this be done?

Is there a Command or Command Group that can be modified?

We don't want our users attaching documents from KM.

I have been digging in xml, jar files, config, etc. Any help would be appreciated and points rewarded!!