Sample Makefile (written for Solaris)
CF_DIR=/usr/lib/mail/
M4=m4

sendmail.cf: sendmail.mc
        ${M4} -D_CF_DIR_=${CF_DIR} ${CF_DIR}m4/cf.m4 sendmail.mc > sendmail.cf
Very simple sendmail.mc (Solaris again)
dnl vim: set syntax=m4 :

divert(0)

OSTYPE(solaris2)

define(`SMART_HOST', `mail.asyd.net')

MAILER_DEFINITIONS
MAILER(local)dnl
MAILER(smtp)dnl
Another simple sendmail.mc (written for Debian)
define(`confSMTP_LOGIN_MSG',`$j Debian (GNU/Linux) / Sendmail')dnl
define(`HELP_FILE', `')dnl
define(`ALIAS_FILE', `/etc/aliases')dnl
  
FEATURE(`masquerade_envelope')dnl
FEATURE(`use_cw_file')dnl
FEATURE(`use_ct_file')dnl
FEATURE(`smrsh')dnl

dnl DNS remote blacklist, use them only for a MX  
FEATURE(`dnsbl', `blackholes.mail-abuse.org')dnl
FEATURE(`dnsbl', `relays.mail-abuse.org')dnl
FEATURE(`dnsbl', `relays.ordb.org')dnl
FEATURE(`dnsbl', `relays.osirusoft.org')dnl

MAILER_DEFINITIONS
MAILER(local)dnl
MAILER(smtp)dnl