General

• Minor note to make AUTH work. in your /usr/ports/mail you'll find some sort of sendmail-sasl dir. Do the appropriate make incantations. Now, most important, you need to change the system default builtin sendmail over to the new one. FreeBSD has installed mailwrapper to do this for you. (Search for mailwrapper at http://www.freebsd.org/) Once this is done, you do not need to mess with /usr/local/etc/rc.d/sendmail.sh or with /etc/rc.conf.
• Use m4. Name your .mc file the hostname-of-this-server.mc
• Consider using the DNS name mail.domainname for mail handling. This allows you to move all mail handling to another server later by merely updating your MX records.
  Corollary: Do not configure a machine with the hostname mail.domainname as this would prevent you from bringing up a new machine, configuring it, and changing over at your leisure by merely changing MX records.
• Use the domain name with hostname for the machine name.:
  this is the confDOMAIN_NAME directive (specifically $j)
  this is very important when you set up your mail secondary machine.
  e.g. my primary machine (brix.vintners.net) has:
  

  define(`confDOMAIN_NAME', `brix.vintners.net')
  

  my secondary machine (vinifera.vintners.net) has:
  

  define(`confDOMAIN_NAME', `vinifera.vintners.net')
  

  Bear in mind that this means mail will only be answered when explicitly sent to this machine (host.domain). On the assumption that you want mail sent simply to the domain to get through, this is an additional domain name -- you will need to add the domain itself to the .cw file (see next step).
• If you wish for sendmail to answer to additional host names for this server:
  
  • Include them in the sendmail.cw (now local-host-names) file.
    e.g. I want my primary server to answer mail to mail.vintners.net so as to avoid ever having an explicit hostname in a mail path. Additionally, I don't want people to have to know that my mail server has a different name:
    sendmail.cw

    vintners.net
    mail.vintners.net
    

  • Be sure to tell sendmail to use the .cw file with:

    define(`confCW_FILE', `/etc/mail/local-host-names')
    FEATURE(`use_cw_file')
    

  • Add them to your MX records as lower cost routes:
    http://www.sendmail.org/~ca/email/english.html (see "mail loops back to myself")
• Bear in mind that sendmail does not deal with customer email readers -- you'll probably want to install popper and/or imap.

Primary machine

• If you are hosting multiple domains
  • You will need to include them in the .cw file.
  • Be sure .cw file is enabled. (See General above)

Secondary machine

• If you start by copying your primary machines .mc file, be sure to change the confDOMAIN_NAME ($j) value. If you don't, you'll get the totally non-helpful: "loops back to me" error. http://www.sendmail.org/faq/section4.html. Months down the line you'll have a terrible time trying to figure this one out.
• Cheap and sleazy
  • Put the main domain name in mailertable and have it point at the primary. This means that this machine will always pass all mail on to the primary for handling.
    If, for example, you were to install majordomo or mailman onto this server so as to offload list processing to an external machine, this configuration would not work as this machine would simply bounce the mail back to the primary instead of handling it.
  More delicate, but better (don't do this 29-Sep-2006)
  • Don't do the previous (do not put the main domain name into mailertable).
  • Do be sure to set up root with a .forward file to point to main machine. Use explicit primary name.
  • Do be sure to set up your main user (that you use to ssh into before su'ing) with a .forward to the primary. As with root, use explicit name to primary.
  • DO put this machine (host.domain) into sendmail.cw (local-host-names)
  • Make sure .cw file is enabled (see General above)
  • If you are hosting multiple domains, the secondary can be treated slightly differently. Simply add entries in the mailertable file to force all mail to said domain to be handled by the primary.
  The right way (29-Sep-2006)
  • Don't do the previous (do not put the main domain name into mailertable).
  • Do be sure to set up root with a .forward file to point to main machine. Use explicit primary name.
  • Do be sure to set up your main user (that you use to ssh into before su'ing) with a .forward to the primary. As with root, use explicit name to primary.
  • Use the confMAIL_HUB directive.
  • Be sure to include this machines name in the primarys local-host-names file.