This sounds like a job for a mail merge. We have an add-on that can do this. https://addons.mozilla.org/en-GB/thunderbird/addon/mail-merge/ One of your challenges is that you'll want to send this message to many contacts, but not show their email addresses to one another. Mail Merge is good for you in that it generates a unique (and possibly personalized) message to each addressee. An alternative is to use a Mailing List, which allows you to concurrently send more messages that are normally allowed by Thunderbird. Here you'd need to use "Bcc:" to hide the addresses, and that has the restriction that the messages won't be addressed "To:" the particular correspondents. In either case, if you're on a small allowance, you may exceed the set limit (probably more so with Mail Merge) and the best answer may be to go to a specialist mass mailer such as Constant Contact or Mailchimp. (I have no direct experience of either of these; they are merely suggestions, not recommendations.)