24.7 SMTP with UUCP

The sendmail configuration that ships with FreeBSD is designed for sites that connect directly to the Internet. Sites that wish to exchange their mail via UUCP must install another sendmail configuration file.

Tweaking /etc/mail/sendmail.cf manually is an advanced topic. sendmail version 8 generates config files via m4(1) preprocessing, where the actual configuration occurs on a higher abstraction level. The m4(1) configuration files can be found under /usr/src/usr.sbin/sendmail/cf.

If you did not install your system with full sources, the sendmail configuration set has been broken out into a separate source distribution tarball. Assuming you have your FreeBSD source code CDROM mounted, do:

# cd /cdrom/src
# cat scontrib.?? | tar xzf - -C /usr/src/contrib/sendmail

This extracts to only a few hundred kilobytes. The file README in the cf directory can serve as a basic introduction to m4(1) configuration.

The best way to support UUCP delivery is to use the mailertable feature. This creates a database that sendmail can use to make routing decisions.

First, you have to create your .mc file. The directory /usr/src/usr.sbin/sendmail/cf/cf contains a few examples. Assuming you have named your file foo.mc, all you need to do in order to convert it into a valid sendmail.cf is:

# cd /usr/src/usr.sbin/sendmail/cf/cf
# make foo.cf
# cp foo.cf /etc/mail/sendmail.cf

A typical .mc file might look like:

VERSIONID(`Your version number') OSTYPE(bsd4.4)

FEATURE(accept_unresolvable_domains)
FEATURE(nocanonify)
FEATURE(mailertable, `hash -o /etc/mail/mailertable')

define(`UUCP_RELAY', your.uucp.relay)
define(`UUCP_MAX_SIZE', 200000)
define(`confDONT_PROBE_INTERFACES')

MAILER(local)
MAILER(smtp)
MAILER(uucp)

Cw    your.alias.host.name
Cw    youruucpnodename.UUCP

The lines containing accept_unresolvable_domains, nocanonify, and confDONT_PROBE_INTERFACES features will prevent any usage of the DNS during mail delivery. The UUCP_RELAY clause is needed to support UUCP delivery. Simply put an Internet hostname there that is able to handle .UUCP pseudo-domain addresses; most likely, you will enter the mail relay of your ISP there.

Once you have this, you need an /etc/mail/mailertable file. If you have only one link to the outside that is used for all your mails, the following file will suffice:

#
# makemap hash /etc/mail/mailertable.db < /etc/mail/mailertable
.                             uucp-dom:your.uucp.relay

A more complex example might look like this:

#
# makemap hash /etc/mail/mailertable.db < /etc/mail/mailertable
#
horus.interface-business.de   uucp-dom:horus
.interface-business.de        uucp-dom:if-bus
interface-business.de         uucp-dom:if-bus
.heep.sax.de                  smtp8:%1
horus.UUCP                    uucp-dom:horus
if-bus.UUCP                   uucp-dom:if-bus
.                             uucp-dom:

The first three lines handle special cases where domain-addressed mail should not be sent out to the default route, but instead to some UUCP neighbor in order to “shortcut” the delivery path. The next line handles mail to the local Ethernet domain that can be delivered using SMTP. Finally, the UUCP neighbors are mentioned in the .UUCP pseudo-domain notation, to allow for a uucp-neighbor !recipient override of the default rules. The last line is always a single dot, matching everything else, with UUCP delivery to a UUCP neighbor that serves as your universal mail gateway to the world. All of the node names behind the uucp-dom: keyword must be valid UUCP neighbors, as you can verify using the command uuname.

As a reminder that this file needs to be converted into a DBM database file before use. The command line to accomplish this is best placed as a comment at the top of the mailertable file. You always have to execute this command each time you change your mailertable file.

Final hint: if you are uncertain whether some particular mail routing would work, remember the -bt option to sendmail. It starts sendmail in address test mode; simply enter 3,0, followed by the address you wish to test for the mail routing. The last line tells you the used internal mail agent, the destination host this agent will be called with, and the (possibly translated) address. Leave this mode by typing Ctrl+D.

% sendmail -bt
ADDRESS TEST MODE (ruleset 3 NOT automatically invoked)
Enter <ruleset> <address>
> 3,0 [email protected]
canonify           input: foo @ example . com
...
parse            returns: $# uucp-dom $@ your.uucp.relay $: foo < @ example . com . >
> ^D