Subject: Linux Electronic Mail HOWTO
From: [email-masked] (Vince Skahan)
Date: Fri, 18 Nov 1994 17:10:44 GMT
Newsgroups: comp.os.linux.announce,comp.os.linux.admin,comp.answers,news.answers

Archive-name: linux/howto/mail
Last-modified: 26 Oct 94

  The Linux Electronic Mail HOWTO
  Vince Skahan, <[email-masked]>
  v1.17, 22 Oct 1994

  This document describes the setup and care+feeding of Electronic Mail
  (e-mail) under Linux.  You need to read this if you plan to communi-
  cate locally or to remote sites via electronic mail.  You probably do
  *not* need to read this document if don't exchange electronic mail
  with other users on your system or with other sites.

  1.  Introduction

  The intent of this document is to answer some of the questions and
  comments that appear to meet the definition of 'frequently asked
  questions' about e-mail software under Linux.

  This document and the corresponding UUCP and News 'HOWTO' documents
  collectively supersede the UUCP-NEWS-MAIL-FAQ that has previously been
  posted to comp.os.linux.announce.

  1.1.  New versions of this document

  New versions of this document will be periodically posted to
  comp.os.linux.announce, comp.answers, and news.answers.  They will
  also be added to the various anonymous ftp sites who archive such
  information including sunsite.unc.edu:/pub/Linux/docs/HOWTO.

  In addition, you should be generally able to find this document on the
  Linux WorldWideWeb home page at http://sunsite.unc.edu/mdw/linux.html
  and on my home page at http://www.halcyon.com/vince/welcome.html.

  1.2.  Feedback

  I am interested in any feedback, positive or negative, regarding the
  content of this document via e-mail.  Definitely contact me if you
  find errors or obvious omissions.

  I read, but do not necessarily respond to, all e-mail I receive.
  Requests for enhancements will be considered and acted upon based on
  that day's combination of available time, merit of the request, and
  daily blood pressure :-)

  Flames will quietly go to /dev/null so don't bother.

  Feedback concerning the actual format of the document should go to the
  HOWTO coordinator - Matt Welsh ([email-masked]).

  1.3.  Copyright Information

  The Mail-HOWTO is copyrighted (c)1994 Vince Skahan.

  A verbatim copy may be reproduced or distributed in any medium
  physical or electronic without permission of the author.  Translations
  are similarly permitted without express permission if it includes a
  notice on who translated it.

  Short quotes may be used without prior consent by the author.
  Derivative work and partial distributions of the Mail-HOWTO must be
  accompanied with either a verbatim copy of this file or a pointer to
  the verbatim copy.

  Commercial redistribution is allowed and encouraged; however, the
  author would like to be notified of any such distributions.

  In short, we wish to promote dissemination of this information through
  as many channels as possible. However, we do wish to retain copyright
  on the HOWTO documents, and would like to be notified of any plans to
  redistribute the HOWTOs.

  We further want that ALL information provided in the HOWTOS is
  disseminated.  If you have questions, please contact Matt Welsh, the
  Linux HOWTO coordinator, at [email-masked].

  1.4.  Standard Disclaimer

  Of course, I disavow any potential liability for the contents of this
  document.  Use of the concepts, examples, and/or other content of this
  document is entirely at your own risk.

  1.5.  Other sources of information

  1.5.1.  LINUX HOWTO Documents:

  There is plenty of exceptional material provided in the other Linux
  HOWTO documents and from the Linux DOC project.  In particular, you
  might want to take a look at the following:

  o  the Serial Communications HOWTO

  o  the Ethernet HOWTO

  o  the Linux Networking Administrators' Guide

  1.5.2.  USENET:

             comp.mail.elm           the ELM mail system.
             comp.mail.mh            The Rand Message Handling system.
             comp.mail.mime          Multipurpose Internet Mail Extensions.
             comp.mail.misc          General discussions about computer mail.
             comp.mail.multi-media   Multimedia Mail.
             comp.mail.mush          The Mail User's Shell (MUSH).
             comp.mail.sendmail      the BSD sendmail agent.
             comp.mail.smail         the smail mail agent.
             comp.mail.uucp          Mail in the uucp environment.

  1.5.3.  Books

  The following is a non-inclusive set of books that will help...

  o  "Managing UUCP and USENET" from O'Reilly and Associates is in my
     opinion the best book out there for figuring out the programs and
     protocols involved in being a USENET site.

  o  "Unix Communications" from The Waite Group contains a nice
     description of all the pieces (and more) and how they fit together.

  o  "Sendmail" from O'Reilly and Associates looks to be the definitive
     reference on sendmail-v8 and sendmail+IDA.  It's a "must have" for
     anybody hoping to make sense out of sendmail without bleeding in
     the process.

  o  "The Internet Complete Reference" from Osborne is a fine reference
     book that explains the various services available on Internet and
     is a great source for information on news, mail, and various other
     Internet resources.

  o  "The Linux Networking Administrators' Guide" from Olaf Kirch of the
     Linux DOC Project is available on the net and is also published by
     (at least) O'Reilly and SSC.  It makes a fine one-stop shopping to
     learn about everything you ever imagined you'd need to know about
     Unix networking.

  1.6.  Where *NOT* to look for help

  There is nothing "special" about configuring and running mail under
  Linux (any more).  Accordingly, you almost certainly do *NOT* want to
  be posting generic mail-related questions to the comp.os.linux.*
  newsgroups.

  Unless your posting is truly Linux-specific (ie, "please tell me what
  routers are already compiled into the SLS1.03 version of smail3.1.28")
  you should be asking your questions in one of the newsgroups or
  mailing lists referenced above.

  Let me repeat that.

  There is virtually no reason to post anything mail-related in the
  comp.os.linux hierarchy any more.  There are existing newsgroups in
  the comp.mail.* hierarchy to handle *ALL* your questions.

  IF YOU POST TO COMP.OS.LINUX.* FOR NON-LINUX-SPECIFIC QUESTIONS, YOU
  ARE LOOKING IN THE WRONG PLACE FOR HELP.  THE ELECTRONIC MAIL EXPERTS
  HANG OUT IN THE PLACES INDICATED ABOVE AND GENERALLY DO NOT RUN LINUX.

  POSTING TO THE LINUX HIERARCHY FOR NON-LINUX-SPECIFIC QUESTIONS WASTES
  YOUR TIME AND EVERYBODY ELSE'S...AND IT FREQUENTLY DELAYS YOU FROM
  GETTING THE ANSWER TO YOUR QUESTION.

  2.  Hardware Requirements

  There are no specific hardware requirements for mail under Linux.

  You'll need some sort of 'transport' software to connect to remote
  systems, which means either tcp-ip or uucp.   This could mean that you
  need a modem or ethernet card (depending on your setup).

  3.  Getting the software

  In general, I grab my sources from ftp.uu.net and the other fine
  archive sites on Internet.  In addition, Linux-specific binary ports
  are found in the usual Linux distrbutions and on the usual Linux
  anonymous ftp sites (sunsite.unc.edu and tsx-11.mit.edu in
  particular).

  The newspak-2.4.tar.z distribution contains config files and readme
  files related to building uucp, news, and mail software under Linux
  from the various freely-available sources.  It can usually be found in
  sunsite.unc.edu:/pub/Linux/system/Mail/news.  If you can't find it on
  sunsite, please send me mail and I'll make sure you get a copy of it.

  4.  Mail 'Transport Agents'

  This section contains information related to 'transport agents', which
  means the underlying software that connects your local system to
  remote systems.

  4.1.  Smail v3.1

  Smail3.1 seems to be a de-facto standard transport agent for uucp-only
  sites and for some smtp sites.  It compiles without patching from the
  sources.  In addition, smail is provided in binary form in the SLS
  distribution of Linux.

  The newspak distribution contains config files for smail3.1.28 under
  Linux that you can use to start with.

  If you're building smail from sources, you need to have the following
  in your os/linux file so that 'sed' gives you shell scripts that work
  properly.

          CASE_NO_NEWLINES=true

  For a uucp-only system that has a MX-record and that wants a
  domainized header (who goes through a smart-host for everything),
  these are the entire config files you'll need:

  o  replace 'subdomain.domain' with your domain name

  o  replace 'myhostname' with you un-domainized hostname

  o  replace 'my_uucp_neighbor' with the uucp name of your upstream site

             #-------- /usr/local/lib/smail/config -----------------
             #
             # domains we belong to
             visible_domain=subdomain.domain:uucp
             #
             # who we're known as (fully-qualified-site-name)
             visible_name=myhostname.subdomain.domain
             #
             # who we go through
             smart_path=my_uucp_neighbor
             #
             #---------- /usr/local/lib/smail/paths --------------
             #
             # we're a domainized site, make sure we accept mail to both names
             myhostname        %s
             myhostname.subdomain.domain      %s
             #
             #-------------------------------------------------------------------

  To run smail as a smtp daemon, add the following to /etc/inetd.conf:

                  smtp stream tcp nowait  root  /usr/bin/smtpd smtpd

  Outgoing mail gets sent automatically, when using elm. If your inter-
  net link is down when you send mail, then the mail sits in
  "/usr/spool/smail/input".  When the link next comes up, "runq" is run
  which causes the mail to be sent.

  4.2.  Sendmail+IDA

  I run a uucp-only site and use sendmail5.67b+IDA1.5 instead of
  smail3.1.28 due to the incredible ease of use.  There is a binary
  distribution in sunsite.unc.edu:pub/Linux/system/Mail/delivery.  To
  install it:

  o  you'll probably want to remove (or rename) all the files from smail
     (see the /install/installed directory if you are SLS) to be safe.

  o  cd to / then "gunzip -c sendmail5.67b+IDA1.5.tpz | tar xvf -" If
     you have a "modern" tar from a recent Slackware (for example) you
     can probably just do a "tar -zxvf filename.tgz" and get the same
     results.

  o  cd to /usr/local/lib/mail/CF and copy the sample.m4 local.m4 file
     to "yourhostname.m4".  Edit out the distributed hostname, aliases,
     and 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 yourhostname.cf" and move
     the resulting file to /etc/sendmail.cf

  o  if you are uucp-only, you do *NOT* need to create any of the tables
     mentioned in the README.linux file.  You'll just have to touch the
     files so that the Makefile works.  Just edit the .m4 file, make
     sendmail.cf, and start testing it.

  o  if you're uucp-only and you talk to sites in addition to your
     "smart-host", you'll need to add uucpxtable entries for each (or
     mail to them will also go through the smart host) and run dbm
     against the revised uucpxtable.

  o  if you use my sendmail5.67b+IDA1.5 distribution you should not use
     a "freeze file".
  o  If you run Rich Braun's original binary distribution of 5.67a,
     you'll need to freeze the configuration if you change your .cf file
     with "/usr/lib/sendmail -bz" to make the changes take effect.  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 may be found at vixen.cso.uiuc.edu.  They
  require no patching to run under Linux if you're running something
  like a kernel of 1.00.

  If you're running a current kernel of around 1.1.50, you get the fun
  of reversing most of the Linux-specific patches that are now in the
  vanilla sources.  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.

  The May/June 1994 edition of Linux Journal has an extensive article on
  the care and feeding of sendmail+IDA.  The new edition of the Linux
  DOC Project Networking Administrator's Guide will have an even more
  detailed and complete version.

  4.2.1.  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(Sendmail.mc)dnl                         # REQUIRED ENTRY !!!
    dnl #
    dnl #------------ END OF SAMPLE SENDMAIL.M4 FILE -------

  4.2.2.  Defining a local mailer

  Unlike most Unix distributions, Linux does not come with a local mail
  delivery agent by default.  I recommend using the commonly available
  deliver program, which is an optional package in a number of the usual
  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 Sendmail.mc file
  that gets included into the sendmail.cf 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, Sendmail.mc 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.

  4.2.3.  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 sendmail.cf file
  directly.  Refer to the July-1994 issue of Linux Journal, 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.

  o  mailertable   - defines special behavior for remote hosts or
     domains.

  o  uucpxtable    - forces UUCP delivery of mail to hosts that are in
     DNS format.

  o  pathtable     - defines UUCP bang-paths to remote hosts or domains.

  o  uucprelays    - short-circuits the pathalias path to well-known
     remote hosts.

  o  genericfrom   - converts internal addresses into generic ones
     visible to the outside world.

  o  xaliases      - converts generic addresses to/from valid internal
     ones.

  o  decnetxtable  - converts RFC-822 addresses to DECnet-style
     addresses.

  4.2.4.  So Which Entries are Really Required?

  When not using any of the optional dbm tables, sendmail+IDA delivers
  mail via the DEFAULT_MAILER (and possibly RELAY_HOST and RELAY_MAILER)
  defined in the sendmail.m4 file used to generate sendmail.cf.  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, and DEFAULT_MAILER.  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 DEFAULT_MAILER to TCP-A and probably delete the
  RELAY_MAILER and RELAY_HOST lines.

  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.

  4.3.  Sendmail 8.6

  Sendmail 8.6.x from Berkeley is the latest major revision after
  sendmail5.  It has wonderful built-in support for building under
  Linux.  Just "make linux" and you'll be all set.

  4.4.  Other "transport agents"

  The following also are known to run under Linux.  Consult "archie" for
  details regarding how to find them...

  o  smail2.5 - very simple UUCP-based smail

  4.5.  Local Delivery Agents

  Unlike most operating systems, Linux does not have mail "built-in".
  You'll need a program to deliver the local mail.  One good program is
  Rich Braun's "lmail" program, but I've switched to using the more
  commonly available "deliver" program.

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

  5.  Mail "User Agents"

  This section contains information related to "user agents", which
  means the software the user sees and uses.  This software relies on
  the "transport agents" mentioned above.

  5.1.  Elm

  Elm compiles, installs, and runs flawlessly under Linux up to and
  through Slackware 1.1.1 (gcc2.4.5, gcclib 4.4.4).  For more
  information, see the elm sources and installation instructions.

  The only thing to know is that Elm's Configure script incorrectly sets
  the "ranlib" variable in config.sh.  The Elm Development Team has been
  informed of this little problem, so please don't bother them with it
  (again).

  o  (from  Chip Rosenthal - [email-masked] ) The easiest way
     to deal with this is to create a file called config.over at the top
     of you Elm source tree and include the line:

             ranlib='ranlib'

  o  Alternatively, you can just remember to correctly edit the line in
     config.sh when Configure gives you the chance to do so.

  o  Elm and filter need to be mode 2755 (group mail) with
     /usr/spool/mail mode 775 and group mail.

     If you use a binary distribution, you'll need to create a
     /usr/local/lib/elm/elm.rc file to override the compiled-in hostname
     and domain information:

  o  replace "subdomain.domain" with your domain name replace

  o  "myhostname" with you un-domainized hostname replace

  o  "my_uucp_neighbor" with the uucp name of your upstream site

             #---------- /usr/local/lib/elm/elm.rc ------------------
             #
             # this is the unqualified hostname
             hostname = myhostname
             #
             # this is the local domain
             hostdomain = subdomain.domain
             #
             # this is the fully qualified hostname
             hostfullname = myhostname.subdomain.domain
             #
             #--------------------------------------------------------

  One thing you want to be aware of is that if you have Elm compiled to
  be MIME-able, you need metamail installed and in your path or Elm will
  not be able to read MIME mail you've received.  Metamail is available
  on thumper.bellcore.com and of course via "archie".

  We have heard reports that gcc and gcclib newer than v2.4.5 and v4.4.4
  respectively are rather strict and fail to compile Elm.  Here's the
  scoop as reported by  [email-masked] (Neil Parker)  who
  forwarded a posting by  [email-masked] (Al Longyear).

  o  ELM is using internal fields in the FILE structure in an effort to
     bypass the standards. (The _flag, _IOERR, and _IOEOF are old fields
     for the pre-POSIX runtime package. While POSIX doesn't say that you
     can't define these fields, it does not say that you _must_. Linux
     does not. It does say that programs should not be written to use
     them, even if they are in the implementation.)

              where it does         if (fp->_flag & _IOERR) ...
              change it to          if (ferror(fp)) ....

              where it does         if (fp->_flag & _IOEOF) ...
              change it to          if (feof(fp)) ...

              These are the ANSI/POSIX definitions for the same function.

  o  While this item is not Linux-specific, it's a nagging bug
     nevertheless.  We've heard that Elm sometimes fails with a message
     that it's unable to malloc() some massive number of bytes.  This
     has been identified as an Elm Bug.  The identified workaround is to
     remove the post-processed global mail aliases (aliases.dir and
     aliases.pag).

  o  (from  [email-masked] (Scot W. Stevenson) )

     The current metamail package requires csh for some of its scripts.
     Failure to have csh (or tcsh) will cause most interesting errors...

  5.2.  Mailx

  There is a fine binary implementation of mailx located on the various
  Linux archive sites.  Make sure you grab version 5.3b or later since
  there are security problems in v5.3a.  If you're into building from
  sources, mailx v5.5 compiles without patching under Linux if you have
  "pmake" installed.

  The only potential problem I'm aware of with the binary distribution
  on sunsite is that it seems to be compiled in a way that requires
  /usr/lib/smail rather than /usr/lib/sendmail as a transport agent.
  You probably need a link if you run sendmail on your system.

  If anybody is still using it, I strongly recommend removing the old
  "edmail" stuff from SLS1.00 and replacing it with mailx.

  5.3.  Other user agents

  The following also are known to run under Linux.  Consult "archie" for
  details regarding how to find them...

  o  Pine      - from the Univ. of Washington

  o  Metamail  - allows MIME support

  o  mh      - yet another way to handle mail

  o  deliver   - file/process mail based on rules

  o  procmail  - file/process mail based on rules

  o  Majordomo - manages e-mail lists

  o  Mserv     - provide files-by-mail

  6.  Acknowledgements

  The following people have helped in the assembly of the information
  (and experience) that helped make this document possible:

  Steve Robbins, Ian Kluft, Rich Braun, Ian Jackson, Syd Weinstein, Ralf
  Sauther, Martin White, Matt Welsh, Ralph Sims, Phil Hughes, Chip
  Rosenthal, Scot Stevenson, Neil Parker

  If I forgot anybody, my apologies...