Qmail is clearly out of compliance with RFC282.

[Marc Perkel <marc@perkel.com>]

From the other thread, the relevant RFC passage was quoted from RFC2821:

   To provide reliable mail transmission, the SMTP client MUST be able
   to try (and retry) each of the relevant addresses in this list in
   order, until a delivery attempt succeeds.


Seems clear to me. Unless you want to argue what MUST means.

   However, there MAY also
   be a configurable limit on the number of alternate addresses that
   can be tried.  In any case, the SMTP client SHOULD try at least two
   addresses.

What this says is that if you decide to have some limits that the limits 
should be set at 2 or more. Since Qmail doesn't have a configurable 
limit then the MUST part applies.
Clearly it is saying that in any case that at least 2 mx records must 
best tested. For some reason you are ignoring the plain language of the 
RFC. It could have been written more precisely but you really have to 
stretch to not get what it is clearly saying.
Qmail is out of compliance with RFC282.