Sendmail + UUCP HOWTO

Author: Jamal Hadi Salim ( or



  • 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 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)
  • DNS and BIND (Publisher O'reilly)
  • TCP/IP Network Administration (Hunt, Craig;Publisher O'reilly)
  • Linux Network Administrator Guide (Olaf Kirch)
  • sendmail Theory and Practice (Avolio and Vixie; publisher Digital press)


    c) how to setup databases (other than the mailertable) to work with sendmail.

    Refer to the many fine references on this, including:
  • The bat book (Sendmail;Costalles, Allman, Rickert -- publisher O'reilly)
  • TCP/IP administration (Publisher O'reilly)
  • Sendmail Theory and Practice (Avolio and Vixie; publisher Digital press)
  • Docs bundled with sendmail d) how to write or modify rulesets or mailers.
  • All the above references  in c)
  • You can also find help on the following newsgroups:
    IRC channels
    #linux, #unix


    This is for a system, hypothecally named, whose mail is sent out only via UUCP. mysmarthost is the ISPs hostname as set up in the uucp sys file and 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., whose setup we describe in the example, feeds sites and and their subnodes. connects to via TCP/IP and connects to 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 
                    |            | *, *, *
                    |            |
                        | UUCP via a phone line receive for 
                        |, *,*,
                        | as well as and *
                    | * *****  *  |
       ------------ | * *  | ------
                    | *        *  |      |
       |            | * *****  *  |      |
       |             ------------        | 
       |UUCP via phone line              | uucp via TCP/IP
       |                                 |
     -----------                  -----------
    |           |                |           |
    ||                |  |-------
    |           |                |           |      |
     ----------                  ------------       |
         |                                          |
         |                                          |
         |                                          | LAN: smtp to nodes
         | UUCP phone line
         |                                          |
    -----------                             -------------
    |         |                             |           |
    |system1's|                             | down's    |
    |subnodes |                             | LAN       |
    |         |                             ------------


    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 (,,
    Edit /etc/hosts and add the following as a sample for the host myhost 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] 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 myhost and NOT myhost you will also need to define the sendmail $w macro to hold
    add the Following line to your /etc/ after it is generated (or you can use MASQUAREADE_AS( 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

    a) No DNS -- standalone

    VERSIONID(`'s setup with uucp created by xxxx --no dns ')
    dnl OSTYPE(linux)
    FEATURE(mailertable, hash /etc/mailertable)dnl
    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(`'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.

  • 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

    VERSIONID(`'s setup with uucp created by xxxx --dns enabled')dnl
    FEATURE(mailertable, hash /etc/mailertable)dnl
    define(`SMART_HOST', uucp-dom:mysmarthost)


    II) create your file

    a) backup your old /etc/ file
    b) overwrite the with the new one: m4 > /etc/
    c) verify that the 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 uucp-dom:system1 uucp-dom:system1 uucp-dom:down  error: Host is unknown at uucp-dom:down error: Host unknown at

    This says anything that is addressed to or to * 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 * ; similar for and its subnodes except for the additional filtering; we bounce back any mail for down's subnode using sendmail's built-in error mailer with the message "Host is unknown at"; This is because we have been asked to do this by the admin at 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!


    1) Add info on setting up system (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.