Well, you may have a few difficulties subscribing to mkcl-devel since common-lisp.net is currently going through yet another great shake up. The mailing lists are back under mailman control again but I have not taken time to update the MKCL web page about it. Here is the link that I should put back:
http://mailman.common-lisp.net/cgi-bin/mailman/listinfo/mkcl-devel
FYI, subscription works also based on your current description. seems like mailman has been configured to be compatible with whatever was used before that.
(i've subscribed by sending a mail to mkcl-devel+subscribe@common-lisp.net and when i tried to subscribe again thorugh the mailmain web interface i got an alert that i'm already subscribed)