The FSF has maintained archives of all of the GNU mailing lists for many years, although there may be some unintentional gaps in coverage. The archive is not particularly well organized or easy to retrieve individual postings from, but pretty much everything is there.
Anonymous FTP:
/prep.ai.mit.edu:/pub/gnu/emacs/MailingListArchives/
{There was a WAIS database named `comp-emacs' on lambada.oit.unc.edu that makes available the last 10 days of articles in comp.emacs. It appears to have died. Anyone know if it moved?}