[Exim] self = ?

Exim 3.13

I have a list of domains, that I want to apply a route_file to, but
ONLY if the MX record for the domain being routed has an MX record that
points to this host.

I currently have this working as follows (except it always catches the
domains in the file, wether the MX record points at us or not)

some_domains:
driver = domainlist
domains = lsearch;/etc/exim/some.domains
route_file = /etc/exim/some.domains
search_type = lsearch
transport = remote_smtp

lookuphost:
driver = lookuphost
transport = remote_smtp


---------------

If I change them as follows, and put lookuphost first, will this
accomplish what I'm trying to do? It seems like it should, from the
paragraph I pasted below about the generic 'self' option..

lookuphost:
driver = lookuphost
transport = remote_smtp
self = fail_soft
no_more

some_domains:
driver = domainlist
domains = lsearch;/etc/exim/some.domains
route_file = /etc/exim/some.domains
search_type = lsearch
transport = remote_smtp


--

self =

.
.
.

- fail_soft

The router fails, passing the address to the following router. During
subsequent routing and delivery, the variable $self_hostname contains
the name of the local host that the router encountered. This can be
used to distinguish between different cases for hosts with multiple
names. This setting overrides a setting of no_more on the router, so a
combination of fail_soft and no_more ensures that only those addresses
that routed to the local host are passed on. Without no_more, failing
addresses would also be passed to the next router.