I gave up, I found all that and just skipped the DCC part. I could not get it to work after I went through everything. The postfix version changed of course so that is another part of the howto that has to change.
In the end, I could send and get e-mail to the machine but never got it to work where I could send mail from another machine using that machine as the smtp, it would fail with SASL auth error (postfix/smtpd warning : SASL Auth failure cannot connect to saslauthd server: permission denied.)
I tried everything I could think of and even re-installed from scratch once, always got that error in the end, found in another post on this site another person for whom "adduser postfix sasl" fixed the problem but it did not for me.
Sure would have liked to upgrade as we are running a ANCIENT 2.2.13 kernel on our mail server and can't even install SpamAssasin on it. I think that kernel is about 10 years old along with the hardware. But for now I have gone back to that since it works.