mimedefang with LDAP-enabled sendmail

[Jonathan McKeown]

I'm hoping someone can point me in the right direction. I'm running 6.1 (the 
security branch) with a recently-updated ports tree (1 September).

I have modified /etc/make.conf to change the options for the system sendmail, 
by adding these lines:

SENDMAIL_CFLAGS = -I/usr/local/include -DSASL=2 -DLDAPMAP
SENDMAIL_LDFLAGS = -L/usr/local/lib
SENDMAIL_LDADD = -lsasl2 -lldap -llber

I have added the necessary ports and rebuilt world: when I run 
ldd /usr/libexec/sendmail/sendmail, I get
        libutil.so.5 => /lib/libutil.so.5 (0x28107000)
        libwrap.so.4 => /usr/lib/libwrap.so.4 (0x28113000)
        libssl.so.4 => /usr/lib/libssl.so.4 (0x2811a000)
        libcrypto.so.4 => /lib/libcrypto.so.4 (0x28148000)
        libsasl2.so.2 => /usr/local/lib/libsasl2.so.2 (0x2823a000)
        libldap-2.3.so.2 => /usr/local/lib/libldap-2.3.so.2 (0x2824f000)
        liblber-2.3.so.2 => /usr/local/lib/liblber-2.3.so.2 (0x2827f000)
        libc.so.6 => /lib/libc.so.6 (0x2828a000)

and sendmail -d0.1 -bt </dev/null gives me

Version 8.13.6
 Compiled with: DNSMAP LDAPMAP LOG MAP_REGEX MATCHGECOS MILTER MIME7TO8
                MIME8TO7 NAMED_BIND NETINET NETINET6 NETUNIX NEWDB NIS
                PIPELINING SASLv2 SCANF STARTTLS TCPWRAPPERS USERDB
                USE_LDAP_INIT XDEBUG

When I try to build and install mail/mimedefang from ports (version is 2.57), 
I get (modulo wrapping)

cc -O2 -fno-strict-aliasing -pipe  -pthread -o mimedefang mimedefang.o 
drop_privs_threaded.o utils.o rm_r.o syslog-fac.o /usr/lib/libmilter.a 
-lpthread
/usr/lib/libmilter.a(errstring.o)(.text+0xd6): In function `sm_errstring':
: undefined reference to `ldap_err2string'
*** Error code 1

Has anyone come across this? (I found a couple of inconclusive entries through 
Google, one on the Mimedefang list from earlier this year, which doesn't seem 
to have attracted an answer, and one from three years ago regarding 
installing MD on Red Hat Linux).

Any suggestions what to try next to get a successful build of mail/mimedefang?

Jonathan