Are they all in one address book? If not, copy them there by drag-and-drop. Now in the address book that contains all your group members, go to '''File|New|Mailing List''' and add them by typing their addresses. (If you can't see the menu, hold down the <alt> key, and tap F for File.) If you can see the address book's Toolbar, it may offer you a button with two heads on it. Give the List a name, but avoid fancy characters; limit yourself to letters, numbers and underscores. I think it best to leave the Description and Nicknames empty. You can, if you prefer, close the Mailing List and it should appear in the address book at the left. Now you can drag and drop your group members onto the List's icon to add them to it. Any time later on when you want to edit your List, double-click it to open its editor. To use your List, enter its name into a message as you would an email address. Note that if you use To:, all the group members' email addresses will be visible to one another. If you don't have their express consent to share their addresses, you should change To: to Bcc: so none of them should see any other addresses. You might like to put your own email address in the To: field to give the recipients a hint of what it's about. Or you could create a new entity to use as the To: address by adding an Identity to your own email account in Thunderbird e.g ''"Mary's Newsletter" <mary@example.com>'' (where "mary@example.com" is your own email address.)