[exim] [EXIM] Condition to vacation autoreply

Hello,
I have a standard transport and router configured that will look for a
message file and a list of recipients that can get the automatic
reply, however I am struggling in solving one problem. I would only
like to respond if the original recipient was not a group defined in
/etc/aliases, however no conditions in the transport work, because the
mail group is by then already expanded to single users. How can I
implement such condition?
Kind regards,
Patryk