>>>>> On Thu, 11 Oct 2007 13:54:40 +1000,
      George Michaelson <ggm@apnic.net> said:

> My reading of this is that the NetBSD current install state for a
> simple postfix instance should not tickle the greylist engine at NetBSD
> more than once. If it does, it suggests we don't back off as much as we
> should..

Your interpretation is not corrent.
That's merely usual greylisting behaviour on mail.netbsd.org,
instead of your MTA, nothing special.

The inital delay of greylisting on mail.netbsd.org is longer than
what you expect, so, the temporary failures must happen more than
once, regardless of the install state of your MTA (well, except for
a case that the MTA is using really long interval for initial retry).

Also, the greylisting database on mail.netbsd.org was recently
refreshed (and will be refreshed again soon for some reason). 
I think that's the reason why the temporary failure happened
against your IP and your mail address.
-- 
soda