Sendmail and DNS lookups

[Gregory P. Ennis]

Everyone,

Thought I could solve this problem, but Looks like I need some help.

I am trying to replace our R.H 8.0 internal e-mail server with a faster
machine using FC3.  I set a FC3 unit up as a desktop PC in order to do
the setup and testing before I put it into production.

I have set up other machines using sendmail with only the usual
problems, but this one has me stumped.  The internal mail server
'mailin.domain.com' needs to pass its e-mail to our external server
'mailout.domain.com' while at the same time processing mailin needs to
process local mail.  

define(`SMART_HOST',`mailp.pomec.net')dnl

The HUB feature was commented because I want it to process some local
mail
dnl define(`MAIL_HUB', `mailp.pomec.com')dnl 

Both of the below are commented out

dnl FEATURE(`accept_unresolvable_domains')dnl
dnl #
dnl FEATURE(`relay_based_on_MX')dnl


I was using the mail coomand in the form of

mail -s 'test trasnmissions to mailout' Name at mailout.com < ./textfile

The maillog on mailin demonstrate that mailout refused the connection.

I checked my host, host.allow files, turned off iptables on both units,
and still no solution.

I decided to watch what was happening using ethereal, and found that
sendmail was doing a dns lookup for domain.com and found the internet IP
address for mailout.domain.com.  Of course when sendmail uses this
address it fails a connection which is related to our firewall.  

I tried using the internal IP address with 'telnet mailout.domain.com
25' and it connects easily.  'telnet "external IP address" 25' does not
connect and this is what sendmail is doing. 

I tried changing the name of of mailout.domain.com in the host file of
mailin to something like mailoutp.domain.com but sendmail continues to
do DNS searches on 'domain.com' giving it the external IP address that
fails.

I need sendmail on the new mailin server to stop doing dns searches for
the IP address and just use the host file for the internal IP address.
I think that would solve this problem.  

I am sure there is a simple solution, but so far I can not find it.
Your help would sure be appreciated.

Thanks,

Greg Ennis


-- 
Gregory P. Ennis <PoMec at PoMec.Net>