[exim] Using the autenticator domain in filter

Hello all.


I have an Exim rule (router) that goes like:


(...)

condition = ${if exists
{/etc/senderlist}{${lookup{$sender_address_domain}lsearch{/etc/senderlist}{0}{1}}}{}}


This works fine as long as the sender doesn't use an alternate "mail from"
header because $sender_address_domain will follow that instead of the true
user domain (i.e., if the joe(at)domain.dom configures his email software
to send mail as johndoe(at)yahoo.com , even if domain.dom is listed at
/etc/senderlist the condition won't match because $sender_address_domain
will be yahoo.com )


The question is: as the email is sent through Exim using authentication,
what is the variable that holds the true user domain and that can be used
in that rule ?


Regards,