[Exim] Matching hostnames in a hostlist

Am I correct that, when I use "hosts = +host_list" in an ACL, and I have
defined "host_list" to include only fully specified hostnames (no wildcards),
then Exim **will not** do a reverse lookup on the connecting host's IP, unless
forced to by something else, right? And this explains why, right after doing
the above check in an ACL, the following statement in the ACL finds that
$sender_host_name is blank?

Now, in general, I avoid doing external DNS lookups whenever possible
(personal philosophy). So I do NOT have "host_lookup = *" set.

Can I simply add "host_lookup = +host_list", even though these are hostnames,
not IPs? And would this then force a lookup for just those hosts in the list?
The ONLY reason I want to do this is to populate $sender_host_name for this
specific list of hosts, so it can be used in a regex later in the ACL.
Otherwise, I am stuck with $sender_helo_name, which is somewhat less reliable,
even though I know the hosts in host_list do EHLO correctly. (I don't want to
be tricked by someone spoofing one of these hostnames in their EHLO.)

Regards,
Jim Roberts
Punster Productions, Inc.