Qmail IPv6
Adding IPv6 support to qmail can be a daunting task. A modern qmail system includes several different components, with various patches and configuration options for each. There are a few patches on the internet that claim to add IPv6 support for a specific component, but I had trouble finding patches for every piece of my qmail install.
I’m not trying to defend IPv6. I realize there are many people with strong feelings towards the subject, including qmail’s author. Switching to IPv6 is a monumental task. It may never happen, but something needs to – we can’t keep NATing forever.
Many software projects have already added support for IPv6. My Gentoo box has been on an IPv6 network, via Hurricane Electric’s free tunnel broker service for a while now. Mac OS X has support for IPv6, as do the latest versions of Windows. Even Windows XP can support IPv6 if enabled. Postfix, Exim, and Sendmail all support IPv6.