The Mailing List is a tool for members to send group emails.

If an Organizer turns on the Mailing List for a Meetup Group, then group members who've sign up for the mailing list can send emails to other subscribers.

A few notes about Mailing Lists:

• The group's Mailing List is completely different from the emails Organizers and Assistant Organizers send as well as the automatic event reminder emails that the site sends. So if you unsubscribe from the group's Mailing List, you will still get event reminder emails as well as emails from the group's Leadership Team.
  
• Only the group members who sign up for the Mailing List will receive emails sent to the Mailing List. So a group may have 100 members, but it's possible that only 80 are on the Mailing List. Only Organizers, Co-Organizers, and Assistant Organizers can see which members are on the Mailing List.
  
• When you send an email to the Mailing List or reply to an email from the Mailing List, every single person on the Mailing List gets a copy. Mailing Lists are for communication between multiple people. Mailing Lists are not for one-to-one communication.

Bear in mind that when you send an email to your Meetup Groups's mailing list, your email address will be disclosed to other members of your Meetup who have also subscribed to the mailing list.