Initial edition July/96: works only with non-bind edition of sendmail
Oct 01 /96: works with the redhat supplied binary
Oct 07 /96: added/modified a tip on how to compile non-bind sendmail
Oct 25 /96: added/modified a tip on how to keep sendmail getHostbyAddr()
happy via a dummy /etc/hosts entry
Mar 15 /97: I am amazed at the response/feedback i am receiving so i decided
to refine this further. Fixed some small errors; added diagram + references.
Oct 25/97: Htmlise+ add blurb on DNS capable machines
After finally settling down and properly reading TFM (the Bat Book,
to be precise) i have solved the Caramilk secret! The steps below have
been tested with the binary supplied by RedHat. Perhaps i should send this
tip to the maintainer of the Sendmail FAQ too since there is absolutely
no mention of UUCP interworking with sendmail there.
What this Document tries to show you
How to setup a single machine, reffered to as me.com in the example,
with no direct access to the internet to route mail for you via sendmail
and UUCP to a 'smarter host' eg your ISP.
Optionally you can configure this machine to feed other machines i.e
you are their 'smart' host or gateway.
What this Document does not tell you
I have been receiving incredible number of questions regarding topics which
are beyond the focus of this HOWTO. The purpose of this document is not
to describe them so please try not send me any questions on the following:
a) How to setup UUCP.
Refer to many fine references on this, including:
UUCP HOWTO (Vince Skahan, )
Using and managing UUCP (Ed Ravin et al -- publisher O'reilly) which i
think is the best authority on UUCP
Linux Network Administrator Guide (Olaf Kirch)
b) how to setup DNS.
Refer to the many fine references on this, including:
Caching named mini howto (Nicolai Langfeldt)
The bat book (Sendmail;Costalles, Allman, Rickert;publisher O'reilly)
This is for a system, hypothecally named me.com, whose mail is sent
out only via UUCP. mysmarthost is the ISPs hostname as set up in
the uucp sys file and me.com is the hostname we use or are
known by in the MX records on the internet.
mysmarthost hooks to the internet. We really dont care how it
does it, we just know it knows how to get us there.
me.com, whose setup we describe in the example, feeds sites
down.com and system1.org and their subnodes. me.com connects
to down.com via TCP/IP and connects to system1.org via raw
UUCP using a phone line.
The setup description is shown below:
------------------------
| |
| Internet |
| |
-----------------------
|
| PPP/dedicated line running TCP-IP
|
-------------
| |
|mysmarthost | Authoritative name server for
| | *.me.com, *.down.com, *.system1.org
| |
--------------
|
| UUCP via a phone line receive for
| system1.org, *.system1.org,*.down.com, down.com
| as well as me.com and *.me.com
------------
| * ***** * |
------------ | * me.com * | ------
| * * | |
| | * ***** * | |
| ------------ |
|UUCP via phone line | uucp via TCP/IP
| |
----------- -----------
| | | |
|system1.org| | down.com |-------
| | | | |
---------- ------------ |
| |
| |
| | LAN: smtp to nodes
| UUCP phone line
| |
----------- -------------
| | | |
|system1's| | down's |
|subnodes | | LAN |
| | ------------
----------
pre-requisites
1) If you are already running DNS or have a
pointer to a DNS server (in your /etc/resolv.conf) and are on a live connection
to the net then skip this part. You are safe. You dont have to do any 'smart'
thing skip to 2) If you are on a machine using uucp for mail then you dont really need
to compile bind/resolv into sendmail;
How to survive name canonicalization on a stand-alone machine with no DNS
PART I If you get a pre-compiled sendmail with BIND in it you can still
live with it (As is the case with Redhat supplied sendmail).
a) Refer to my solution for this based on the m4 file described (my
favorite). Try to use this option unless you really insist on b) or c)
below OR
b)If you talk to me i could supply you with a non-BIND compiled version
(8.8.5). Perhaps RedHat should consider supplying two sendmail binaries
(like slakware) One with BIND and the other with no BIND. OR
c) The quickest solution to get sendmail with no bind is to edit src/conf.h
lines below to read as i have shown:
# ifndef NAMED_BIND conf.h:# define NAMED_BIND 0 /* use Berkeley
Internet Domain Server */
PART II:
Sendmail would however normally insist on doing name look ups to resolve
the host part using gethostbyaddr() for each email it sends (even
if you tell it not to canonify names).
a) use an RFC1597 IP address (10.0.0.0-10.255.255.255, 172.16.0.0-172.31.255.255,
192.168.0.0-192.168.255.255)
Edit /etc/hosts and add the following as a sample for the host
myhost
10.0.0.1 myhost.me.com myhost or
b) If you use NIS (and NIS is compiled into sendmail as seems to be
the case in Redhat. ) make sure the /etc/nsswitch.conf file contains:
hosts: files dns and in /etc/hosts and add the following
as a sample for the host myhost [again using RFC1597 IP addressing scheme]
10.0.0.1 myhost.me.com myhost
NOTE: ---- In both a) and b) above it is critical that you list
the long (fully qualified) in the /etc/hosts file used. i.e the line should
read 10.0.0.1 myhost.me.com myhost and NOT 10.0.0.1 myhost you
will also need to define the sendmail $w macro to hold myhost.me.com add the Following line to your /etc/sendmail.cf after it is
generated Djmyhost.me.com (or you can use MASQUAREADE_AS(myhost.me.com)
in the .mc below)
NOTE!!!!! myhost as a domain name is given as an example;
you dont have to use it as is. Pick your own hostname if you dont have
one already.
2) Ensure that you have makemap and it is
capable of supporting hash and or the more common dbm format or even
btree format (The Redhat version does not support dbm). Makemap is normaly
distributed with sendmail.
SETUP (the mc file)
I) create your .mc file using your favorite editor; i'll call this file
my.mc
a) No DNS -- standalone
include(`../m4/cf.m4') VERSIONID(`me.com's setup with uucp created by xxxx --no dns ') dnl OSTYPE(linux) FEATURE(nodns)dnl FEATURE(nocanonify)dnl FEATURE(always_add_domain)dnl FEATURE(mailertable, hash /etc/mailertable)dnl MAILER(local)dnl MAILER(smtp)dnl MAILER(uucp) define(`SMART_HOST', uucp-dom:mysmarthost)
Let's dissect this:
include(`../m4/cf.m4') requests for the m4 macro found in ../m4/cf.m4
to be include to resolve some things
VERSIONID(`me.com's setup with uucp created by xxxx')dnl This
is used to distinguish the different versions of .cf file you might end
up creating.
OSTYPE(linux) This is used to define/redefine linux specific stuff.
It is safe to have it here.
FEATURE(nodns)dnl This says we dont have a DNS server (so in effect
we are using uucp only for mail. Sendmail must be compiled not to use bind)
This is now obsolete. I will let it stay here just in case you use an older
version of sendmail.
FEATURE(nocanonify)dnl This says Don't pass addresses to $[ ...
$] for canonification. Normally if you have BIND compiled in sendmail
would try and expand the alias/IP address to a canonical name using DNS.
You dont wanna do this if all you have are feeds which connect to you via
UUCP i.e you are a stand alone.
FEATURE(always_add_domain)dnl This adds the local domain host name
even on locally delivered mail Not necessary i just like it; This
might not be a safe feature since spammers, with proper setup conditions,
can abuse you.
me.com is not connected to the net via tcp/ip so it is safe
FEATURE(mailertable, hash /etc/mailertable)dnl the file /etc/mailertable
is going to be a hash database where we will store routing information
of certain sites. If you dont have anyone who you feed uucp to then you
dont need this. More on this later. If you wanted to use the dbm format
you would have FEATURE(mailertable, dbm /etc/mailertable)dnl If
you wanted to use the btree format you would have FEATURE(mailertable,
btree /etc/mailertable)dnl
MAILER(local)dnl MAILER(smtp)dnl MAILER(uucp) These are the mailers
we use.
define(`SMART_HOST', uucp-dom:mysmarthost) Our smart host is our
ISP who is defined in the uucp sys file as system mysmarthost.
Any messages that we cant handle (i.e ones for domains or mailers we dont
understand) will be passed on to our smarthost/ISP to figure out. note
we use uucp-dom as the uucp mailer. This particular mailer uses smtp
rewriting rules.
b) DNS on
include(`../m4/cf.m4') VERSIONID(`me.com's setup with uucp created by xxxx --dns enabled')dnl OSTYPE(linux) FEATURE(always_add_domain)dnl FEATURE(mailertable, hash /etc/mailertable)dnl MAILER(local)dnl MAILER(smtp)dnl MAILER(uucp) define(`SMART_HOST', uucp-dom:mysmarthost)
II) create your sendmail.cf file
a) backup your old /etc/sendmail.cf file
b) overwrite the sendmail.cf with the new one: m4 my.mc > /etc/sendmail.cf c) verify that the sendmail.cf file was correctly created based on
your specifications.
Some of the gotchas that i came across were: - missing uucp-dom
mailer This was because i didnt have the smtp mailer entry. Actually,
i understand it is important to have it defined before the uucp
III) create your /etc/mailertable
if you dont have uucp sites feeding off you skip this step
a) create/edit the file /etc/mailertable
sample /etc/mailertable
system1.org uucp-dom:system1 .system1.org uucp-dom:system1 down.com uucp-dom:down up.down.com error: Host is unknown at me.com .down.com uucp-dom:down .me.com error: Host unknown at me.com
This says anything that is addressed to system1.org or to *.system1.org
that we receive will be sent using the uucp-dom mailer and be
delivered to system1 (defined in the the uucp sys file) in
other words we are doing the mail routing for *.system1.org ; similar
for down.com and its subnodes except for the additional filtering;
we bounce back any mail for down's subnode up.down.com using sendmail's
built-in error mailer with the message "Host is unknown at
me.com"; This is because we have been asked to do this by the admin
at down.com. To bounce unknown subdomains to us we use the last
line in the mailertable (which is what all unknown nodes default to).
b) create the database with makemap
if you use hash:
makemap hash /etc/mailertable < /etc/mailertable if you use dbm: makemap dbm /etc/mailertable </etc/mailertable if you use btree: makemap btree /etc/mailertable </etc/mailertable
do this every time you change the file.
IV) restart sendmail
V) test sendmail
i) sendmail -bv user@destination
ii) using sendmail -bt and enter various addresses using 3,0
ruleset to see where they end up and the various rulesets and cf walks
taken.
You are set!
TODO
1) Add info on setting up system down.com (so as to show how to
take care of those smtp nodes)
2) Add info on how to setup news to be delivered via UUCP
(preferably INN). This might require changing the title of the doc.
