replying to a message of a mailing list you were not subscribed to

[Danny Milosavljevic]

> Even worse, if I want to reply to an issue on a mailing list that I'm not
> subscribed to, it's difficult. I still haven't figured it out, maybe you can 
> go
> to the archive and download an mbox and look at the reference and ask your 
> mail
> client to reply to it? I don't know.

You read the (X-)"Message-Id" header field from the archive (for Guix, it's in 
a HTML comment - for example in 
<http://lists.gnu.org/archive/html/guix-devel/2016-07/msg01127.html>). Then you 
add an "In-Reply-To" header with the same value to your E-Mail (if your E-Mail 
client doesn't add angle brackets, add them manually - but for example git 
send-email adds angle brackets automatically).

I'd suggest to make this field a text in the archive instead of a comment. Is 
that possible?