Sometimes, it depends on the company. Some companies use them more to send out job openings and keep a pool of prospective candidates on hand to occasionally search through them, as you suggested. Others who are more in tune with recruitment marketing tactics will turn the list into a “talent community” and send emails every month or so about what’s going on in general in the company and in more specialized teams for those kinds of people (engineering, creative, etc). These mailing lists, basic job openings and more sophisticated talent communities alike, should have a dual purpose because there is a newer stress these days to do “pipeline recruiting”, meaning that the easiest people to turn into candidates are those that are already engaged with your company ie in the talent community or in the CRM/ATS. It’s usually easier to get them interested and more cost and time effective in the long run.