I have a list for an organization with around 250 contacts. Because Thunderbird has a mailing limit of around 60, I have divided this list into 5 separate address books. (AB 1, AB 2, etc.) But I see that each address book can have separate mailing lists and I think that would be a better way to go forward. So instead of having 5 address books, I would have 1 with 5 mailing lists But I cannot find a way to move or copy the 50 contacts in the individual address books into one of the specific mailing lists. I can move the contacts from each of the existing 5 address books into a single address book – but that leaves me with the original issue. How can I move these contacts into 5 separate mailing lists under 1 address book?