yyenc should be something that can be handled in a .mailcap file if the right entry is used. Then pine would be able to handle those files by viewing and saving them. pan is a graphical news reader specifically for kde. Once a good .mailcap entry is done, any newsreader that supports mime ought to be able to deal with these files. The speakup goodies have a mailcap-stuff.tar.gz file but I don't think it has anything for yyenc though.
