here is an updated copy of the configuration/shared/webassist/UniversalEmail/xml/WAUniversalEmail.xml that should correct the problem.
see the Common Installation Issues PDF here for details on locating the configuration folder:
common_installation_issues.pdf
after updating this file, delete the cache file from as outlined in the common_installation_issues.pdf, then reopen Dreamweaver, on the page that sends the email, open the server behaviors panel, double click the Universal Email server behavior to edit it and click ok to have the code regenerated, then re upload the entire WA_UniversalEmail folder to the server.