diff --git a/postfix/HISTORY b/postfix/HISTORY
index baaf4922a..d535f378f 100644
--- a/postfix/HISTORY
+++ b/postfix/HISTORY
@@ -27078,3 +27078,29 @@ Apologies for any names omitted.
 	Cleanup: in the PostgreSQL client, cosmetic changes to make
 	the code easier to maintain (in preparation for adding new
 	functionality). File: global/dict_pgsql.c.
+
+20230428
+
+	Bugfix (defect introduced: Postfix 1.0): the command 'postconf
+	.. name=v1 .. name=v2 ..' (multiple instances of the same
+	parameter name) created multiple name=value entries with
+	the same parameter name. It now logs a warning and skips
+	the earlier update. Found during code maintenance. File:
+	postconf/postconf_edit.c
+
+	Bugfix (defect introduced: Postfix 3.3): the command 'postconf
+	-M name1/type1='name2 type2 ..." died with a segmentation
+	violation when the request matched multiple master.cf
+	entries. The master.cf file was not damaged. Problem reported
+	by SATOH Fumiyasu. File: postconf/postconf_master.c.
+
+20230502
+
+	Bugfix (defect introduced: Postfix 2.11): the command
+	'postconf -M name1/type1="name2 type2 ...'" could add a
+	service definition to master.cf that conflicted with an
+	already existing service definition. It now replaces all
+	existing service definitions that match the service pattern
+	'name1/type1' or the service name and type in 'name2 type2
+	...' with a single service definition 'name2 type2 ...'.
+	Problem reported by SATOH Fumiyasu. File: postconf/postconf_edit.c.
diff --git a/postfix/proto/stop.spell-history b/postfix/proto/stop.spell-history
index 096da091a..ccaef1f1f 100644
--- a/postfix/proto/stop.spell-history
+++ b/postfix/proto/stop.spell-history
@@ -56,3 +56,5 @@ Valgrind
 Florian
 Piekert
 refactored
+Fumiyasu
+SATOH
diff --git a/postfix/src/global/mail_version.h b/postfix/src/global/mail_version.h
index 775fa2a8c..202583f12 100644
--- a/postfix/src/global/mail_version.h
+++ b/postfix/src/global/mail_version.h
@@ -20,7 +20,7 @@
   * Patches change both the patchlevel and the release date. Snapshots have no
   * patchlevel; they change the release date only.
   */
-#define MAIL_RELEASE_DATE	"20230419"
+#define MAIL_RELEASE_DATE	"20230502"
 #define MAIL_VERSION_NUMBER	"3.9"
 
 #ifdef SNAPSHOT
diff --git a/postfix/src/postconf/Makefile.in b/postfix/src/postconf/Makefile.in
index 6aff794aa..f872b8aae 100644
--- a/postfix/src/postconf/Makefile.in
+++ b/postfix/src/postconf/Makefile.in
@@ -55,7 +55,8 @@ tests: test1 test2 test3 test4 test5 test6 test7 test8 test9 test10 test11 \
 	test31 test32 test33 test34 test35 test36 test37 test39 test40 test41 \
 	test42 test43 test44 test45 test46 test47 test48 test49 test50 test51 \
 	test52 test53 test54 test55 test56 test57 test58 test59 test60 test61 \
-	test62 test63 test64 test65 test66 test67 test68 test69 test70 test71
+	test62 test63 test64 test65 test66 test67 test68 test69 test70 test71 \
+	test72 test73 test74 test75
 
 root_tests:
 
@@ -989,6 +990,54 @@ test71:	$(PROG) test71.ref
 	diff test71.ref test71.tmp
 	rm -f main.cf master.cf test71.tmp
 
+# Different requests to add lines to master.cf.
+test72:	$(PROG) test72.ref
+	rm -f main.cf master.cf
+	touch main.cf master.cf
+	./postconf -Mc. smtp/unix='smtp unix - n n - 0 other'
+	./postconf -Mc. smtp/abcd='smtp fifo - n n - 0 other'
+	./postconf -Mc. smtp/abcd='smtp inet - n n - 0 other'
+	touch -t 197201010000 main.cf
+	$(HTABLE_FIX) $(SHLIB_ENV) $(VALGRIND) ./$(PROG) -Mc. >test72.tmp 2>&1
+	diff test72.ref test72.tmp
+	rm -f main.cf master.cf test72.tmp
+
+# Replace one entry based on the name+type in the request's service entry.
+test73:	$(PROG) test73.ref
+	rm -f main.cf master.cf
+	touch main.cf master.cf
+	./postconf -Mc. smtp/unix='smtp unix - n n - 0 other'
+	./postconf -Mc. smtp/abcd='smtp fifo - n n - 0 other'
+	./postconf -Mc. smtp/abcd='smtp inet - n n - 0 other'
+	./postconf -Mc. smtp/abcd='smtp unix - n n - 0 otherx'
+	touch -t 197301010000 main.cf
+	$(HTABLE_FIX) $(SHLIB_ENV) $(VALGRIND) ./$(PROG) -Mc. >test73.tmp 2>&1
+	diff test73.ref test73.tmp
+	rm -f main.cf master.cf test73.tmp
+
+# Replace one entry based on the name+type in the request's service pattern.
+test74:	$(PROG) test74.ref
+	rm -f main.cf master.cf
+	touch main.cf master.cf
+	./postconf -Mc. smtp/unix='smtp unix - n n - 0 other'
+	./postconf -Mc. smtp/abcd='smtp fifo - n n - 0 other'
+	./postconf -Mc. smtp/abcd='smtp inet - n n - 0 other'
+	./postconf -Mc. smtp/fifo='lmtp unix - n n - 0 otherx'
+	touch -t 197401010000 main.cf
+	$(HTABLE_FIX) $(SHLIB_ENV) $(VALGRIND) ./$(PROG) -Mc. >test74.tmp 2>&1
+	diff test74.ref test74.tmp
+	rm -f main.cf master.cf test74.tmp
+
+# Warn about skipping redundant name=value update.
+test75:	$(PROG) test75.ref
+	rm -f main.cf master.cf
+	touch main.cf master.cf
+	./postconf -c. mail_version=x mail_version=y >test75.tmp 2>&1
+	touch -t 197501010000 main.cf
+	$(HTABLE_FIX) $(SHLIB_ENV) $(VALGRIND) ./$(PROG) -nc. >>test75.tmp 2>&1
+	diff test75.ref test75.tmp
+	rm -f main.cf master.cf test75.tmp
+
 printfck: $(OBJS) $(PROG)
 	rm -rf printfck
 	mkdir printfck
@@ -1184,6 +1233,7 @@ postconf_main.o: postconf_main.c
 postconf_master.o: ../../include/argv.h
 postconf_master.o: ../../include/check_arg.h
 postconf_master.o: ../../include/dict.h
+postconf_master.o: ../../include/dict_ht.h
 postconf_master.o: ../../include/htable.h
 postconf_master.o: ../../include/mail_params.h
 postconf_master.o: ../../include/master_proto.h
diff --git a/postfix/src/postconf/postconf_edit.c b/postfix/src/postconf/postconf_edit.c
index eb57cc8b5..7085acd72 100644
--- a/postfix/src/postconf/postconf_edit.c
+++ b/postfix/src/postconf/postconf_edit.c
@@ -192,6 +192,11 @@ void    pcf_edit_main(int mode, int argc, char **argv)
 	} else {
 	    msg_panic("pcf_edit_main: unknown mode %d", mode);
 	}
+	if ((cvalue = htable_find(table, pattern)) != 0) {
+	    msg_warn("ignoring earlier request: '%s = %s'",
+		     pattern, cvalue->value);
+	    htable_delete(table, pattern, myfree);
+	}
 	cvalue = (struct cvalue *) mymalloc(sizeof(*cvalue));
 	cvalue->value = edit_value;
 	cvalue->found = 0;
@@ -456,8 +461,38 @@ void    pcf_edit_master(int mode, int argc, char **argv)
 
 	    /*
 	     * Match each service pattern.
+	     * 
+	     * Additional care is needed when a request adds or replaces an
+	     * entire service definition, instead of a specific field or
+	     * parameter. Given a command "postconf -M name1/type1='name2
+	     * type2 ...'", where name1 and name2 may differ, and likewise
+	     * for type1 and type2:
+	     * 
+	     * - First, if an existing service definition a) matches the service
+	     * pattern 'name1/type1', or b) matches the name and type in the
+	     * new service definition 'name2 type2 ...', remove the service
+	     * definition.
+	     * 
+	     * - Then, after an a) or b) type match, add a new service
+	     * definition for 'name2 type2 ...', but only after the first
+	     * match.
+	     * 
+	     * - Finally, if a request had no a) or b) type match for any
+	     * master.cf service definition, add a new service definition for
+	     * 'name2 type2 ...'.
 	     */
 	    for (req = edit_reqs; req < edit_reqs + num_reqs; req++) {
+		PCF_MASTER_ENT *tentative_entry = 0;
+		int     use_tentative_entry = 0;
+
+		/* Additional care for whole service definition requests. */
+		if ((mode & PCF_MASTER_ENTRY) && (mode & PCF_EDIT_CONF)) {
+		    tentative_entry = (PCF_MASTER_ENT *)
+			mymalloc(sizeof(*tentative_entry));
+		    if ((err = pcf_parse_master_entry(tentative_entry,
+						      req->edit_value)) != 0)
+			msg_fatal("%s: \"%s\"", err, req->raw_text);
+		}
 		if (PCF_MATCH_SERVICE_PATTERN(req->service_pattern,
 					      service_name,
 					      service_type)) {
@@ -503,18 +538,30 @@ void    pcf_edit_master(int mode, int argc, char **argv)
 			     * Replace entire master.cf entry.
 			     */
 			case PCF_MASTER_ENTRY:
-			    if (new_entry != 0)
-				pcf_free_master_entry(new_entry);
-			    new_entry = (PCF_MASTER_ENT *)
-				mymalloc(sizeof(*new_entry));
-			    if ((err = pcf_parse_master_entry(new_entry,
-						     req->edit_value)) != 0)
-				msg_fatal("%s: \"%s\"", err, req->raw_text);
+			    if (req->match_count == 1)
+				use_tentative_entry = 1;
 			    break;
 			default:
 			    msg_panic("%s: unknown edit mode %d", myname, mode);
 			}
 		    }
+		} else if (tentative_entry != 0
+			 && PCF_MATCH_SERVICE_PATTERN(tentative_entry->argv,
+						      service_name,
+						      service_type)) {
+		    service_name_type_matched = 1;	/* Sticky flag */
+		    req->match_count += 1;
+		    if (req->match_count == 1)
+			use_tentative_entry = 1;
+		}
+		if (tentative_entry != 0) {
+		    if (use_tentative_entry) {
+			if (new_entry != 0)
+			    pcf_free_master_entry(new_entry);
+			new_entry = tentative_entry;
+		    } else {
+			pcf_free_master_entry(tentative_entry);
+		    }
 		}
 	    }
 
diff --git a/postfix/src/postconf/postconf_master.c b/postfix/src/postconf/postconf_master.c
index 3606ac70c..bddb1af25 100644
--- a/postfix/src/postconf/postconf_master.c
+++ b/postfix/src/postconf/postconf_master.c
@@ -156,6 +156,7 @@
 #include <readlline.h>
 #include <stringops.h>
 #include <split_at.h>
+#include <dict_ht.h>
 
 /* Global library. */
 
@@ -395,12 +396,12 @@ const char *pcf_parse_master_entry(PCF_MASTER_ENT *masterp, const char *buf)
 	concatenate("ro", PCF_NAMESP_SEP_STR, masterp->name_space, (char *) 0);
     masterp->argv = argv;
     masterp->valid_names = 0;
+    masterp->ro_params = dict_ht_open(ro_name_space, O_CREAT | O_RDWR, 0);
     process_name = basename(argv->argv[PCF_MASTER_FLD_CMD]);
-    dict_update(ro_name_space, VAR_PROCNAME, process_name);
-    dict_update(ro_name_space, VAR_SERVNAME,
-		strcmp(process_name, argv->argv[0]) != 0 ?
-		argv->argv[0] : process_name);
-    masterp->ro_params = dict_handle(ro_name_space);
+    dict_put(masterp->ro_params, VAR_PROCNAME, process_name);
+    dict_put(masterp->ro_params, VAR_SERVNAME,
+	     strcmp(process_name, argv->argv[0]) != 0 ?
+	     argv->argv[0] : process_name);
     myfree(ro_name_space);
     masterp->all_params = 0;
     return (0);
diff --git a/postfix/src/postconf/test72.ref b/postfix/src/postconf/test72.ref
new file mode 100644
index 000000000..6b13cdcbd
--- /dev/null
+++ b/postfix/src/postconf/test72.ref
@@ -0,0 +1,3 @@
+smtp       unix  -       n       n       -       0       other
+smtp       fifo  -       n       n       -       0       other
+smtp       inet  -       n       n       -       0       other
diff --git a/postfix/src/postconf/test73.ref b/postfix/src/postconf/test73.ref
new file mode 100644
index 000000000..9554cc074
--- /dev/null
+++ b/postfix/src/postconf/test73.ref
@@ -0,0 +1,3 @@
+smtp       unix  -       n       n       -       0       otherx
+smtp       fifo  -       n       n       -       0       other
+smtp       inet  -       n       n       -       0       other
diff --git a/postfix/src/postconf/test74.ref b/postfix/src/postconf/test74.ref
new file mode 100644
index 000000000..288633496
--- /dev/null
+++ b/postfix/src/postconf/test74.ref
@@ -0,0 +1,3 @@
+smtp       unix  -       n       n       -       0       other
+lmtp       unix  -       n       n       -       0       otherx
+smtp       inet  -       n       n       -       0       other
diff --git a/postfix/src/postconf/test75.ref b/postfix/src/postconf/test75.ref
new file mode 100644
index 000000000..b8c54abe0
--- /dev/null
+++ b/postfix/src/postconf/test75.ref
@@ -0,0 +1,3 @@
+./postconf: warning: ignoring earlier request: 'mail_version = x'
+config_directory = .
+mail_version = y