Author: Rik Thomas
Email: rikt@delug.org
Web Page: http://www.delug.org
Date Submitted: Mon, Jan 4, 1999
Status: New Entry

Requester: Ray
Email: ray@clark.net
Web Page: http://www.clark.net/pub/ray
Request Made: Tue, Mar 17, 1998

Releases: all
Platform: all
Category:  Email
Category Listing:  Email on a small Lan between machines ?

Issue

I have been asked this question several times now and don't 
really have a good answer. I am using a DNS setup on my Lan so 
this is not a problem for me, however quite a few people with 
only two or three machines have a real problem with this. How do 
you setup sendmail to be able to send email between machines on 
a small Lan using RedHat 5.0 ? RedHat has a small description of how 
to do this in their manual on page 107 using one machine as the 
mail gateway, but since Sendmail distributed with RedHat depends 
on DNS, how does someone setup sendmail to allow this service 
without having DNS ? Thanks for any info, 

Response

You basically have two ways to handle this. Through DNS and/or a 
HOSTS file. However sendmail should sense that the mail should be 
handled through the local MDA. That is part of ruleset 0. See the 
Bat(Sendmail) book at http://sysadmin.oreilly.com.
First you need to ensure (for ease of routing since this is a 
small lan) that each client has an IP on the same subnet. Then you 
need to ensure that each user has an account on the mail server. 
Next you need to make sure that each has a valid host name and 
all are using the same domain. Distribute a master hosts file to 
all clients. Make sure their DNS points to a valid DNS server, if 
it is a small lan it should be the mail server too. Make sure 
there is a relevant entry in DNS for all machines as well. NOTE: 
Using just a hosts file will work just as well. Make sure that 
all clients mail programs point to the mail server for sending 
mail and receiving mail. Make sure you are running pop3 or qpopper 
(or whatever Pop/IMAP server you wish) and there you go. This should 
get you up and running with a great internal/external mail system 
for a small LAN. For more advanced mail routing see the bat book 
and investigate diald for internet mail routing on a 
non-dedicated connection to the internet. 

References

(none)