I just subscribed to a mailing list that (still) requests that messages sent to it be text-only, no exceptions. (Their FAQ references storage space being at a premium on PDAs such as Palm Pilots.) Sooner or later, I'll probably forget to do this, assuming I'm setting this for each message. Is it possible to set up Gmail to automatically default to text-only when composing or replying to a specific listserv? 
Set Gmail to reply text-only to only a specific address
gmail;text