[Exim] Mail for domain address

Hi

I'm just starting with Exim. I want to setup a serwer that handles mail for
given domain (for example domain.com.pl). Exim is placed on server named
'host'. All users are served by the aliasfile director:

local_users:
        driver          = aliasfile
        include_domain  = no
        search_type     = pgsql
        query           = "SELECT mailbox FROM mail_user WHERE
id_user='${local_part}' AND domain='${domain}'"
        transport       = local_store

Host is beeing prepared to handle more then one domain. Unfortunately all
mail that should get to domain.com.pl have its domain set do
host.domain.com.pl (with hostname attached).

The entry in DNS also seems to be correct:

IN MX 10 host.domain.com.pl

How can force exim to see the domain properly?

Przem