Well, honestly the structure of your script is completely up to you, you can read in from the text file, cache the results and send MIME:Lite into a loop and send the bulk of your mail, if you do it as a CGI script, I'd imagine that you'd want it pretty much like an admin script that has a big button that you hit and sends an email to everyone in your list. If you're asking about having to use CGI to e-mail, no as long as you have a working mailer on the computer you're running the script on. Either way it's up to you. Please post code if you have a specific logic/syntax problem.
BlackJudas
Update: Cross-post from deleted node.