sendmail: using sendmail as submitting MTA

[O. Hartmann]

We use a monitoring server (icinga2) based on FreeBSD embedded in a closed
network (no external access) with a M$ mailexchange server.

I try to configure local sendmail in a way so that all email going to the
localhost are delivered to the local machine itself, but email for an external
email account is passed to the mail hub server. This mail hub server is
accessible by any host in the closed network without authentication (this is
given by a higher instance as a fact I can not change).

I tried to figure out with the recent handbook but the explanation of how to
configure sendmail is really poor. Since I'm not that familiar with sendmail
itself anymore, I appreciate some startups here.

As I understand the docs, the files 

hostname.localdomain.mc

and 

hostname.localdomain.submit.mc

are the only ones I need to touch, along with

mailertable

for the resolution of the target domain and the mail-hub server to contact.

The target email domain would be foobar.bla, so I use an entry in mailertable
like

foobar.bla	esmtp:[IP4] (no MX record usage)
.foobar.bla	esmtp:[IP4]

There is no suitable access to a DNS for MX resolution (all Microsoft crap), so
I have an /etc/host entry for the mailhub server - or mail relaying server. But
nothing works so far. Checking the mail queue with mailq gives me always on all
outbound emails

host map: lookup (foobar.bka): deferred

What is wrong?

Please CC me, I' do not subscribe this specific list.

Thank you in advance,

Oliver

P.S. I ggoled for that specific error and got lots of how-tos but it seems that
none of them worked so far. I guess I miss something. I already did a 

make all install 

in /etc/mail after every change.