Despite the fact that it is documented in the handbook, the release notes,

and UPDATING and has been posted to both freebsd-current and
freebsd-stable, users are still not adding the required smmsp user and
group before doing an installworld.  Therefore, don't let users do an
installworld unless they have followed directions.

Add a new installcheck Makefile target which installworld runs before
actually starting the installation.  This target can be used by other parts
of userland as well.  The first addition to the target is to check for the
smmsp user and group if NO_SENDMAIL isn't defined.

Others may add checks to this target as they see fit.

MFC after:	1 week

Makefile

@@ -84,9 +84,9 @@
 #
 TGTS=	afterdistribute all all-man buildkernel buildworld checkdpadd clean \
 	cleandepend cleandir depend distribute distribworld everything \
-	hierarchy includes install installkernel kernel reinstallkernel \
-	installmost installworld libraries lint maninstall mk most obj \
-	objlink regress rerelease tags update
+	hierarchy includes install installcheck installkernel kernel \
+	reinstallkernel installmost installworld libraries lint maninstall \
+	mk most obj objlink regress rerelease tags update
 
 PATH=	/sbin:/bin:/usr/sbin:/usr/bin
 MAKE=	PATH=${PATH} make -m ${.CURDIR}/share/mk -f Makefile.inc1

Makefile.inc1

@@ -312,12 +312,29 @@ everything:
 	@echo "--------------------------------------------------------------"
 	cd ${.CURDIR}; ${WMAKE} all
 
+#
+# installcheck
+#
+# Checks to be sure system is ready for installworld
+#
+installcheck:
+.if !defined(NO_SENDMAIL)
+	@if ! `grep -q '^smmsp:' /etc/passwd`; then \
+		echo "ERROR: Required smmsp user is missing, see /usr/src/UPDATING."; \
+		false; \
+	fi
+	@if ! `grep -q '^smmsp:' /etc/group`; then \
+		echo "ERROR: Required smmsp group is missing, see /usr/src/UPDATING."; \
+		false; \
+	fi
+.endif
+
 #
 # installworld
 #
 # Installs everything compiled by a 'buildworld'.
 #
-installworld:
+installworld: installcheck
 	mkdir -p ${INSTALLTMP}
 	for prog in [ awk cat chflags chmod chown date echo egrep find grep \
 	    ln make makewhatis mkdir mtree mv perl rm sed sh sysctl \