Yahoo mail

I want to compact, or as yahoo puts it, archive my mail. The
instructions for doing that are simple enough. My problem
is that when I go to mail options, the option to archive is
not there. I've only e-mailed yahoo mail support 3 times
for help, so I guess they have an excuse for ignoring me.
Can anyone help. Archived mail is returned as a zip and
can be removed from yahoo mail to make room. Any
suggestions on zipping mail or getting yahoo's attention
would be appreciated. Thanks, ell.