Find a Listserv and set up a discussion there that sends out email to all subscribers. If yours is an arts type of association you may find a municipal setup or a university that offers free access to a discussion list. They can be moderated or wide open, and you can set them up so you approve all posts, meaning you see the spam but it doesn't go through because you don't approve it. And you can set up a spam filter to catch most of that.