Postfix 2.2
The book covers the patches to postfix for IPv6 support. However, postfix 2.2 is now here and supports IPv6 (and TLS) without the need for any patches. I upgraded a mail system using postfix over the weekend and found the process remarkably painless. Having read the IPV6_README file that came with postfix I discovered that I really only needed to make one change to main.cf, which was to tell postfix to listen on any inet protocol by using the directive inet_protocols = all.
The new IPv6 code even spotted a mistake in my original configuration file and logged a helpful error message: fatal: non-null host address bits in "2001:db8:ee0:cc01::/48", perhaps you should use "2001:db8:ee0::/48" instead! Seems to have been a nice integration of the work of Dean Strik and others into the Postfix mainline.