I’ve been trying unsuccessfully to get the &cc feature to work for over an hour now, going through the source code of eform and the class.phpmailer.php file. I can’t find the problem, but my workaround was to use the &bcc parameter instead. In this particular case that workaround was acceptable, but I know that it won’t be acceptable in all cases.
The nonfunctional &cc parameter seems to be a longstanding problem. See for example this thread:
http://modxcms.com/forums/index.php/topic,9211.0.html
Any progress on this issue would be very welcome.