[exim] query re smtp_banner, smtp_active_hostname and $domai…

hi all
I'm new to most things mail and all things exim. I've successfully set
up a hosting facility that functions according to the second definition
of 'virtual domain' in chp 46.6 of docs, i.e:

"One of a number of independent domains that are all handled by the same
host, with mailboxes on that host, but where the mailbox owners do not
necessarily have login accounts on that host"

I use $local_part and $domain extensively to query postgres and
determine authentication and maildir locations etc.

However, if I "telnet myhost.org 25" I get the primary_hostname back in
the smtp banner. for example, the domains myhost.org, mydomain.com may
be both hosted, and regardless of whether the user comes in as
myhost.org or mydomain.com, I get the same banner back.

What I would like is the equivalent of $domain expanded back in the
banner - which I understand doesnt exist at this time. I've had a look
things like smtp_active_hostname etc, but it seems that the best I can
do reverse lookup the ip and derive it that way, which in my context is
uselss.

Is this possible? Its probably not a BIG deal, but I want to get my
dnsreport.com results with no red boxes on them :-)

Thanks
Glenn