Reply-To Automunging

Sometimes I have ideas for bits of software and think “that’s a great idea, but I’ll never get around to implementing it”. So, rather than let this particular one go to waste, I’m posting it here to see if someone wants to pick it up and run with it.

For many, many years there has been a flamewar between those mailing-list users who think Reply-To munging is considered harmful, and those who think it is considered useful.

For those who don’t know, Reply-To munging is when mailing list software changes the Reply-To header on list mail to point to the list. It’s a “holy war” – people have entrenched positions, no-one ever changes their mind, and it’s rare to find a list populated with solely one or the other type. I’d argue that the mungers are the majority, but maybe that’s because I’m one ;-)

Anyway, here’s the idea: a Thunderbird extension which allows you to define the behaviour of the Reply (note: not Reply All) button based on whether the email is from a mailing list or not. It would either reply to the From: address, the To: address or the Reply-To: address, depending on whether you would have preferred the list to be munged or un-munged. Here’s a little table of which header to use:

My Preference
List Is Munged


List Is Unmunged


I Like Munged Reply-To To (i.e. not From)
I Like Unmunged From (i.e. not Reply-To) From

So the extension would have a single bit of configuration – whether you like your lists munged or unmunged. It would then detect mailing list messages based on email headers, such as any of the List-* ones defined by RFC 2919 and RFC 2369, and make the Reply button magically do the right thing without any further hassle.

(Now, if only there were as simple a solution to the tabs-vs-spaces controversy…)

9 thoughts on “Reply-To Automunging

  1. The Majordomo2 list software (what we use on will let each user choose which way they want it on their list subscription. I don’t know whether Mailman does this yet or not (the one we run on doesn’t, but it’s old).

  2. An extension author trying to implement such a scheme would hit the first obstacle when trying to access the headers… The mailnews core only sends the default To/From/Date etc. headers to chrome, unless the user has enabled the “View all headers” mode (supposedly for performance reasons). So extensions that want to use other headers must briefly switch to all headers, then back to normal, which is a quite ugly and instable hack, especially when multiple extensions that mess with that setting are installed. There’s a bug filed to change this – let’s all hope it gets fixed soon.

  3. I guess if this is an extension, the “leave it as is” option isn’t necessary.. I’d get confused because I’ve learned to expect certain lists to operate certain ways. (i’d get confused because I don’t always use thunderbird; I also use Apple on the notebook).

    OTOH, I guess I’m an un-munger, and I’d like to be able to reply to the sender of a mail, and thunderbird doesn’t presently make this easy to do. (Reply to Sender still goes to the list)..

  4. This is hilarious, thanks for sharing! I had no idea what munging was, nor had I ever heard of it, but for some reason it made me laugh and for that I am thankful.

    Happy Munging!

  5. talking about lists, I am missing a great deal of features when it comes to lists management.

    Something that allows me to keep track of the mailing lists I am subscribed to, with an auto subscribe feature (auto-reply the inscription email), auto-unsubscribe (keep track of the email headers), etc…

  6. jens.b: Good point, although From, To and Reply-To are already sent. But yes, you’d have trouble determining whether a message was a list message or not. In the mean time, you could ask the user to explicitly specific the addresses of the lists they are subscribed to.

  7. It would surely be better to use the List-Post address from the headers than to use the From address?

    An alternative system would be to add a “Reply to List” button when a message from a list is selected, and change the default “Reply” button to “Reply to Sender”. Then depending on the preference, map the Ctrl-R shortcut to the appropriate one.

  8. David: it’s certainly true that you need both Reply to List and Reply to Sender options, and that Ctrl-R and the Reply button need to do the correct one. Perhaps there should be a second button called Reply to Sender or Reply To List, depending on what Reply does for you…

    Using List-Post, if present, for the top-right box does indeed seem very sensible.