[Exim] Reading the nameserver info from remote host

Just a thought in the never ending battle against spam.

Whould it be possible - or could it be added to exim - a way to look up
the nameservers of a given host? In other words - when a host connects
to deliver email - I want to know what name server has the authority
over the domain it is coming from - or perhaps claim to come from.

If I am a spammer and I've registered domains - I have to point those
domains at my own name server which has a fixed IP address. Maybe there
is a clue there for identifying spam.

Anyhow - like I said - it may not go anywhere but it just makes me
wonder - and if Exim had the capability I could start doing some
nameserver lookups and see if there's something useful. If nothing else
- maybe to find and abuse email address and email them automatically.

Something like nameserver(expression) would return a string with a list
of IP addresses of who is the authority for the IP passed or the domain
passed.

I might even parse out links to images within a spam and look up the
nameserver that has authority for thise images.

Any thoughts on this?