Hi,
So I have two things I would like to address which I have realised:
Firstly is the fact that Arch Linux almost always picks IPv4 over IPv6 when delivery the mail. I am aware this is not a big issue because I still receive the email but Arch Linux has full support for IPv6, and I would like to have it used (especially for the hope in the future we can all use single stack IPv6 and get rid of legacy IPv4).
as you can see in the headers, the MTA sending mails is not mailman itself, but Postfix. As I got your mail via IPv6, I think it's just the default behaviour of Postfix: http://www.postfix.org/postconf.5.html#smtp_address_preference As pointed out in the docs, setting ipv6 as preference is considered unsafe. As an IPv6 enthusiast, I had set my Postfix to ipv6 myself and remember some issues with broken MX. Regards Bjoern