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5. Sendmail+IDA

For big sites, sendmail is worth choosing, due to the incredible ease of use, but you must decide which you want between sendmail+IDA and sendmail 8.x :

Remember, linux newbies or people concerned by security / ease of configuration should rather try using smail or qmail, which are easier to use and safer.

5.1 Source installation

Edit out the distributed hostname, aliases, smarthost and put in the correct one for your site. The default file is for a uucp-only site who has domainized headers and who talks to a smart host. Then "make" and move the resulting file to /etc/

You'll just have to touch the files so that the Makefile works. Just edit the .m4 file, make and start testing it.

You should also update your version to at least 5.67b since there is a nasty security hole in 5.67a and earlier. Another nice thing is that if you have mail.debug set and you run syslogd, your incoming and outgoing mail messages will get logged. See the "/etc/syslog.conf" file for details.

The sources for sendmail+IDA can be found at ; they require no patching to run under Linux if you're running something like a kernel of 1.00.

If you're running a kernel > 1.1.50, you get the fun of reversing most of the Linux-specific patches that are now in the vanilla sources. (I *did* told you this sendmail was only for old kernels :-)

It's extremely obvious where this needs to be done : just type "make" and when it blows up, go to that line in the sources and comment out the Linux-specific code that's in there.

If you're going to run sendmail+IDA, I strongly recommend you go to the sendmail5.67b+IDA1.5 version since all required Linux-specific patches are now in the vanilla sources and several security holes have been plugged that WERE (!!!) in the older version you may have grabbed or built before about December 1st, 1993.

Now linux kernel is 2.0, you should use sendmail 8.x insted of sendmail+IDA, but I told you'd better choose sendmail 8.x :-)

5.2 The sendmail.m4 file

Sendmail+IDA requires you to set up a sendmail.m4 file rather than editing the sendmail.cffile directly. The nice thing about this is that it is simple to set up mail configurations that are extremely difficult (if not totally impossible for most people to set up correctly) in smail or traditional sendmail.

The sendmail.m4 file that corresponds to the above smail example looks like the following:

  dnl #------------------ SAMPLE SENDMAIL.M4 FILE ------------------
  dnl #
  dnl # (the string 'dnl' is the m4 equivalent of commenting out a line)
  dnl #
  dnl # you generally don't want to override LIBDIR from the compiled in paths
  dnl #define(LIBDIR,/usr/local/lib/mail)dnl    # where all support files go
  define(LOCAL_MAILER_DEF, mailers.linux)dnl    # mailer for local delivery
  define(POSTMASTERBOUNCE)dnl                   # postmaster gets bounces
  define(PSEUDODOMAINS, BITNET UUCP)dnl         # don't try DNS on these
  dnl #
  dnl #-------------------------------------------------------------
  dnl #
  dnl # names we're known by
  define(PSEUDONYMS, myhostname.subdomain.domain myhostname.UUCP)
  dnl #
  dnl # our primary name
  define(HOSTNAME, myhostname.subdomain.domain)
  dnl #
  dnl # our uucp name
  define(UUCPNAME, myhostname)dnl
  dnl #
  dnl #-------------------------------------------------------------
  dnl #
  define(UUCPNODES, |uuname|sort|uniq)dnl       # our uucp neighbors
  define(BANGIMPLIESUUCP)dnl                    # make certain that uucp
  define(BANGONLYUUCP)dnl                       #  mail is treated correctly
  define(RELAY_HOST, my_uucp_neighbor)dnl       # our smart relay host
  define(RELAY_MAILER, UUCP-A)dnl               # we reach moria via uucp
  dnl #
  dnl #--------------------------------------------------------------------
  dnl #
  dnl # the various dbm lookup tables
  dnl #
  define(ALIASES, LIBDIR/aliases)dnl            # system aliases
  define(DOMAINTABLE, LIBDIR/domaintable)dnl    # domainize hosts
  define(PATHTABLE, LIBDIR/pathtable)dnl        # paths database
  define(GENERICFROM, LIBDIR/generics)dnl       # generic from addresses
  define(MAILERTABLE, LIBDIR/mailertable)dnl    # mailers per host or domain
  define(UUCPXTABLE, LIBDIR/uucpxtable)dnl      # paths to hosts we feed
  define(UUCPRELAYS, LIBDIR/uucprelays)dnl      # short-circuit paths
  dnl #
  dnl #--------------------------------------------------------------------
  dnl #
  dnl # include the 'real' code that makes it all work
  dnl # (provided with the source code)
  dnl #
  include(                         # REQUIRED ENTRY !!!
  dnl #
  dnl #------------ END OF SAMPLE SENDMAIL.M4 FILE -------

5.3 Defining a local mailer

Unlike most Unix distributions, Linux does not come with a local mail delivery agent by default. Now, deliver or procmail is generally installed, so no complexity will be added to this already very complex setup. I recommend using the commonly available deliver or procmail programs, which can be optional packages in a some Linux distributions.

In order to do so, you need to define a LOCAL_MAILER_DEF in the sendmail.m4 file that points to a file that looks like:

  # -- /usr/local/lib/mail/mailers.linux --
  #     (local mailers for use on Linux )
  Mlocal, P=/usr/bin/deliver, F=SlsmFDMP, S=10, R=25/10, A=deliver $u
  Mprog,  P=/bin/sh,       F=lsDFMeuP,   S=10, R=10, A=sh -c $u

There is a also built-in default for deliver in the file that gets included into the file. To specify it, you would not use the mailers.linux file but would instead define the following in your sendmail.m4 file:

   dnl --- (in sendmail.m4) ---
   define(LOCAL_MAILER_DEF, DELIVER)dnl       # mailer for local delivery

Unfortunately, assumes deliver is installed in /bin, which is not the case with Slackware1.1.1 (which installs it in /usr/bin). In that case you'd need to either fake it with a link or rebuild deliver from sources so that it resides in /bin. Please note procmail is generally better than deliver, for example for mail filtering.

5.4 The sendmail+IDA dbm tables

Setting up special behavior for sites or domains is done through a number of optional dbm tables rather than editing the file directly.

Refer to the July-1994 issue of Linux Journal (if you can still find it :-), to the docs in the sources, or to the sendmail chapter in the newest version of the Linux DOC Project Networking Administration Guide which will be available real-soon-now for more details.

5.5 So which entries are really required?

When not using any of the optional dbm tables, sendmail delivers mail via the RELAY_HOST and RELAY_MAILER) defined in the sendmail.m4 file used to generate It is easily possible to override this behavior through entries in the domaintable or uucpxtable.

A generic site that is on Internet and speaks Domain Name Service, or one that is UUCP-only and forwards all mail via UUCP through a smart RELAY_HOST, probably does not need any specific table entries at all.

Virtually all systems should set the DEFAULT_HOST and PSEUDONYMS macros, which define the canonical site name and aliases it is known by.

If all you have is a relay host and relay mailer, you don't need to set these defaults since it works automagically. UUCP hosts will probably also need to set UUCPNAME to their official UUCP name.

They will also probably set RELAY_MAILER and RELAY_HOST which enable smart-host routing through a mail relay.

The mail transport to be used is defined in RELAY_MAILER and should usually be UUCP-A for UUCP sites. If your site is SMTP-only and talks `Domain Name Service', you would change the RELAY_MAILER.

If you're a SLIP site, you might want to take the easy way out and just forward all outgoing mail to your service provider to do the right thing with. To do so, you'd want to define ISOLATED_DOMAINS and VALIDATION_DOMAINS to be your domain, you'd also want to define RELAY_HOST to be your service provider and RELAY_MAILER to be TCP. Of course, you want to ask permission before you set any system up as your general purpose relay.

5.6 Sendmail 8.x

Sendmail 8.7.x from Berkeley was the latest major revision after sendmail5. It had wonderful built-in support for building under Linux : just "make linux" and all was set.

You'll probably be best served by grabbing one of the various binary distributions off of the usual Linux archive sites rather than fighting things like Berkeley dbm yourself.

There's a nice distribution of sendmail 8.6.12 from Jason Haar - j.haar at on in /pub/Linux/system/Mail/delivery/sendmail-8.6.12-bin.tgz that has the source documentation and a very nice quickie description of how to run sendmail v8 for common configurations.

The bottom line with sendmail v8 is that you want to configure the bare minimum necessary to get the job done ; the following is an example that should get you close at least.

5.7 A sample 8.7.x mc file

Much like sendmail+IDA, sendmail v8 uses m4 to process a config file into a full that sendmail uses. The following is my current mc file for my site (ppp to Internet for outgoing mail, uucp for incoming mail).

        dnl divert(-1)
        # this is the .mc file for a linux host that's set up as follows:
        #       - connected to Internet for outbound mail (ppp here)
        #       - connected via UUCP for incoming mail
        #       - domainized headers
        #       - no local mailer (use 'deliver' instead)
        #       - no DNS running so don't canonicalize outgoing via DNS
        #       - all non-local outbound mail goes to the RELAY_HOST over smtp
        #           (we run ppp and let our service provider do the work)
        #                                       vds 3/31/95
        VERSIONID(`linux nodns relays to slip service provider smarthost')dnl
        Cwmyhostname.myprimary.domain myhostname.UUCP localhost
        dnl MAILER(local)dnl
        define(`LOCAL_MAILER_PATH', `/bin/deliver')
        define(`LOCAL_MAILER_ARGS', `deliver $u')

5.8 Sendmail v8 tidbits

There are a few differences I suppose to the 'IDA bigots' among us. So far, I've found the following:

Instead of 'runq', you type 'sendmail -q' to run the queue !

5.9 Local Delivery Agents

Unlike most operating systems, Linux did not have mail "built-in" : you needed a program to deliver the local mail, like "lmail", "procmail" or "deliver".

However, every recent distribution includes a local mailer !

Documentation for how to use either for local delivery is in the sendmail5.67b+IDA1.5 binary release (on sunsite) mentioned above.

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