Is 'additional section' cached?

[Simon Waters]

"Clifton T. Sharp Jr." wrote:
> 
> I do a 'dig telocity.com. mx' and the answer snaps back in an instant.
> Then I try to use the address for inbound.telocity.com.criticalpath.net,
> and my server *repeatedly* times out looking for it. Does the server only
> cache *some* addresses it receives in the 'additional section' of the reply?

It will only cache stuff it trusts. Not sure how much of
that applies here.

The real problem is that 2 of their 3 name servers aren't
answering ns1 and ns2 (At least not from here). They don't
answer for telocity.com or telocity.net.

So in my case the first look up failed completely, and I
really don't want to analyse the innards of a query that is
forced into such a tortuous route.