Unclear: apparently they do but some more than others. A recent conference hosted by the Congressional Management Foundation was dedicated to replacing the misinformation, misperceptions, and frustrations about communications between Members of Congress and citizens with solid research and a collaborative process. One key take away finding was: “Many congressional staff doubt the legitimacy of identical form communications, and want to know whether communications are sent with constituents’ knowledge and consent.” For information on what was discussed see
http://www.cmfweb.org/index.php?option=com_content&task=view&id=231