diff --git a/etc/emqx.conf b/etc/emqx.conf
index dc039c199..f302af423 100644
--- a/etc/emqx.conf
+++ b/etc/emqx.conf
@@ -525,20 +525,20 @@ zone.external.idle_timeout = 15s
 
 ## Publish limit for the external MQTT connections.
 ##
-## Value: rate,burst
-## Default: 10 messages per second, and 100 messages burst.
-## zone.external.publish_limit = 10,100
-
-## Enable ban check.
-##
-## Value: Flag
-zone.external.enable_ban = on
+## Value: Number,Duration
+## Example: 10 messages per minute.
+zone.external.publish_limit = 10,1m
 
 ## Enable ACL check.
 ##
 ## Value: Flag
 zone.external.enable_acl = on
 
+## Enable ban check.
+##
+## Value: Flag
+zone.external.enable_ban = on
+
 ## Enable per connection statistics.
 ##
 ## Value: on | off
@@ -766,7 +766,7 @@ listener.tcp.external.zone = external
 ##
 ## Value: rate,burst
 ## Unit: Bps
-## listener.tcp.external.rate_limit = 1024,4096
+listener.tcp.external.rate_limit = 1024,4096
 
 ## The access control rules for the MQTT/TCP listener.
 ##
diff --git a/priv/emqx.schema b/priv/emqx.schema
index c5afd9b43..2aa0a35a1 100644
--- a/priv/emqx.schema
+++ b/priv/emqx.schema
@@ -676,14 +676,14 @@ end}.
   {datatype, {enum, [allow, deny]}}
 ]}.
 
-%% @doc Enable Ban.
-{mapping, "zone.$name.enable_ban", "emqx.zones", [
+%% @doc Enable ACL check.
+{mapping, "zone.$name.enable_acl", "emqx.zones", [
   {default, off},
   {datatype, flag}
 ]}.
 
-%% @doc Enable ACL check.
-{mapping, "zone.$name.enable_acl", "emqx.zones", [
+%% @doc Enable Ban.
+{mapping, "zone.$name.enable_ban", "emqx.zones", [
   {default, off},
   {datatype, flag}
 ]}.
@@ -696,7 +696,6 @@ end}.
 
 %% @doc Publish limit of the MQTT connections.
 {mapping, "zone.$name.publish_limit", "emqx.zones", [
-  {default, undefined},
   {datatype, string}
 ]}.
 
@@ -850,6 +849,15 @@ end}.
                     {mqtt_wildcard_subscription, Val};
                ("shared_subscription", Val) ->
                     {mqtt_shared_subscription, Val};
+               ("publish_limit", Val) ->
+                    [Limit, Duration] = string:tokens(Val, ", "),
+                    PubLimit = case cuttlefish_duration:parse(Duration, s) of
+                                   Secs when is_integer(Secs) ->
+                                       {list_to_integer(Limit) / Secs, list_to_integer(Limit)};
+                                   {error, Reason} ->
+                                       error(Reason)
+                               end,
+                    {publish_limit, PubLimit};
                ("force_gc_policy", Val) ->
                     [Count, Bytes] = string:tokens(Val, "| "),
                     GcPolicy = case cuttlefish_bytesize:parse(Bytes) of
@@ -862,12 +870,12 @@ end}.
                ("force_shutdown_policy", Val) ->
                     [Len, Siz] = string:tokens(Val, "| "),
                     ShutdownPolicy = case cuttlefish_bytesize:parse(Siz) of
-                                   {error, Reason} ->
-                                       error(Reason);
-                                   Siz1 ->
-                                         #{message_queue_len => list_to_integer(Len),
-                                           total_heap_size   => Siz1}
-                               end,
+                                         {error, Reason} ->
+                                             error(Reason);
+                                         Siz1 ->
+                                             #{message_queue_len => list_to_integer(Len),
+                                               total_heap_size   => Siz1}
+                                     end,
                     {force_shutdown_policy, ShutdownPolicy};
                (Opt, Val) ->
                     {list_to_atom(Opt), Val}