[Exim] failed to find host name from IP address - exim_rejec…

I've just upgraded our primary mail server to exim from sendmail and am just
having trouble with one aspect of its configuration.

I am getting errors in the reject_log similar to the following:

2000-07-12 09:38:33 refused relay (host) to <rachel.dent@???> from
<simon.kay@???> H=(barringtons.uk.net) [212.159.24.108]
(failed to find host name from IP address)

The lowest value MX for barringtons.uk.net is
primary.mail.barringtons.uk.net which has IP 194.201.48.11, the same as the
primary mail server's, whose actual name is bravo.whitburn.xcalibre.co.uk -
I hope it is not this that is confusing matters!

I read the FAQ (Q0029) which suggested trying exim -bh 212.159.24.108 - I
enclose the output of that here:

[root@bravo:/usr/local/exim/log]# ../bin/exim -bh 212.159.24.108

**** SMTP testing session as if from host 212.159.24.108
**** Not for real!

>>> host in host_lookup? no (option unset)
>>> host in host_reject? no (option unset)
>>> host in host_reject_recipients? no (option unset)
>>> host in sender_unqualified_hosts? no (option unset)
>>> host in receiver_unqualified_hosts? no (option unset)
>>> host in helo_verify? no (option unset)
>>> host in helo_accept_junk_hosts? no (option unset)
220 bravo.whitburn.xcalibre.co.uk ESMTP Exim 3.15 #1 Wed, 12 Jul 2000
11:35:50 +0100
mail from: simon.kay@???
>>> simon.kay@??? in sender_reject? no (option unset)
>>> simon.kay@??? in sender_reject_recipients? no (option
unset)
250 <simon.kay@???> is syntactically correct
rcpt to: rachel.dent@???
>>> ic24.net in local_domains? no (end of list)
>>> ic24.net in relay_domains? no (end of list)
>>> looking up host name for 212.159.24.108
>>> IP address lookup failed
>>> host in host_accept_relay? no (failed to find host name or lookup
deferred)
550 relaying to <rachel.dent@???> prohibited by administrator (failed
to find host name from IP address)
LOG: refused relay (host) to <rachel.dent@???> from
<simon.kay@???> H=[212.159.24.108] (failed to find host name
from IP address)

I then stumbled upon the "host_reject = +warn_unknown" option - so I put
that in the configuration file and restarted exim. I expected this to make
exim accept emails where it couldn't lookup the other server's hostname, but
to log it. However, the situation was unchanged, and the mail was still
being rejected.

I enclose the relevant part of my exim configuration file below.

MYSQL_AUTHSERVER=echo.whitburn.xcalibre.co.uk
MYSQL_AUTHPORT=3306
MYSQL_AUTHDB=xcalibre
MYSQL_AUTHTABLE=email
MYSQL_AUTHUSER=admin
MYSQL_AUTHPASSWORD=test
MYSQL_USERNAMEFIELD=username
MYSQL_DOMAINFIELD=domain
MYSQL_ALIASFIELD=alias
MYSQL_ISALIASFIELD=is_alias
RELAY_TIMEOUT=5 MINUTE
MYSQL_ALIAS = SELECT MYSQL_ALIASFIELD FROM MYSQL_AUTHTABLE WHERE
MYSQL_DOMAINFIELD LIKE '${quote_mysql:$domain}' AND MYSQL_USER$
MYSQL_ALL_ALIAS = SELECT MYSQL_ALIASFIELD FROM MYSQL_AUTHTABLE WHERE
MYSQL_DOMAINFIELD='${quote_mysql:$domain}' AND MYSQL_USERN$
MYSQL_USER = SELECT DISTINCT MYSQL_DOMAINFIELD FROM MYSQL_AUTHTABLE WHERE
MYSQL_DOMAINFIELD LIKE '${quote_mysql:$domain}' AND M$
MYSQL_DOMAIN = SELECT DISTINCT MYSQL_DOMAINFIELD FROM MYSQL_AUTHTABLE WHERE
MYSQL_DOMAINFIELD='$key'
MYSQL_RELAY = SELECT ip FROM relay_ip WHERE ip="${sender_host_address}" AND
DATE_SUB(NOW(), INTERVAL RELAY_TIMEOUT) < ts
mysql_servers =
"MYSQL_AUTHSERVER::MYSQL_AUTHPORT/MYSQL_AUTHDB/MYSQL_AUTHUSER/MYSQL_AUTHPASS
WORD"

LOCAL_DOMAINS = localhost:bravo.whitburn.xcalibre.co.uk
primary_hostname = bravo.whitburn.xcalibre.co.uk
local_domains = LOCAL_DOMAINS:mysql;MYSQL_DOMAIN
forbid_domain_literals
never_users = root
host_accept_relay = localhost:mysql;MYSQL_RELAY
host_reject = +warn_unknown
rbl_domains = rbl.maps.vix.com:relays.orbs.org

I hope that somebody will be able to point me in the correct direction!

Best wishes,

Ollie Cook