Add \'/usr/bin/mozilla -compose\' --- --- Probably before this way of invoking Mozilla was not supported. For this reason or another, Mozilla composer has not yet been included in the list. Now a cmd like mozilla -compose \'<a href="mailto:imz@lrn.ru" target="_new">imz@lrn.ru</a>\' works fine.
fixed in urlview-0.9-ipl4mdk. (Now there is a separate file for the lists of handler-programs: /etc/urlview/url_handlers. And it has a user analogue: ~/.etc/urlview/url_handlers.)