Hmm, strange. It is working in the demo site. Here are the links on both my test and your demo sites:

http://mydomain.com/webmail.cgi?&nh=2

http://freemail.gossamer-threads.com/webmail.cgi?sid=ee7cd02048c57f746eb84a369c3b6280&t=default&msgtrack_fid=1&nh=2

I am using default templates on both.

Which version is running demo site? Is it running under mod_perl?

Luck,
TukBa