Absolutely! You can temporarily disable the Motitags menu bar from appearing in your webmail compose window by clicking the "ON/OFF" button located on your Motitag toolbar.
At this you cannot turn off Motitags for individual services while leaving it running for others. If turned off, Motitags will not appear in any webmail compose window.
While we hope you keep Motitags for emails around forever, should you wish to uninstall the Motitags toolbar, you can find instructions for doing so here: