Conditionally build directories depending on protocols that may be disabled.

@@ -5,10 +5,18 @@
 AUTOMAKE_OPTIONS = gnu 1.6 readme-alpha
 ACLOCAL_AMFLAGS = -I m4
 
+# directories depending on mh support
+MH_DIRS = mh
+MH_BUILD_DIRS = @MH_BUILD_DIRS@
+
+# directories depending on the smtp protocol
+SMTP_DIRS = mail.remote
+SMTP_BUILD_DIRS = @SMTP_BUILD_DIRS@
+
 SUBDIRS = include m4 lib testsuite mailbox examples doc \
           auth frm from pop3d imap4d \
           mail sieve scripts libmu_scm guimb messages comsat readmsg \
-          mail.local mail.remote dotlock mh
+          mail.local $(SMTP_BUILD_DIRS) dotlock $(MH_DIRS)
 
 EXTRA_DIST = mailutils.spec mailutils.spec.in COPYING.FDL