Did you get the list instructions when you signed on?

Here are the instructions for signing off:

The listserv address:  [log in to unmask]

    This is the address to which you sent your subscription request,
    and it should be used for all requests that can be handled
    automatically by the LISTSERV program.  This includes changing
    your name or address, unsubscribing, changing your subscription
    options, retrieving files from the file server, searching the list
    archives, etc.  You will find a list of the most commonly used
    LISTSERV commands in the next section.

SIGNOFF NO-MILK

This command removes you from the NO-MILK list.
If you are forced to change Internet providers and cannot unsubscribe
from your old e-mail address, please send an e-mail note to the
listowner and he will unsubscribe you from your old e-mail address.