diff --git a/modoboa/admin/__init__.py b/modoboa/admin/__init__.py
index 09093b61c..85571fdad 100644
--- a/modoboa/admin/__init__.py
+++ b/modoboa/admin/__init__.py
@@ -33,24 +33,29 @@ parameters.register_admin(
     help=ugettext_lazy("The backend used for authentication")
 )
 parameters.register_admin(
-    "CREATE_DIRECTORIES", type="list_yesno", deflt="yes",
-    help=ugettext_lazy("Modoboa will handle mailbox creation on filesystem")
+    "LDA", type="list", deflt="dovecot",
+    values=[('dovecot', "Dovecot"), ('postfix', 'Postfix')],
+    help=ugettext_lazy("Local Delivery Agent")
 )
 parameters.register_admin(
     "STORAGE_PATH", type="string", deflt="/var/vmail",
+    visible_if="LDA=postfix",
     help=ugettext_lazy("Path to the root directory where messages are stored")
 )
 parameters.register_admin(
     "VIRTUAL_UID", type="string", deflt="vmail", modify_cb=update_uid,
+    visible_if="LDA=postfix",
     help=ugettext_lazy("UID of the virtual user which owns domains/mailboxes/messages on the filesystem")
 )
 parameters.register_admin(
     "VIRTUAL_GID", type="string", deflt="vmail", modify_cb=update_gid,
+    visible_if="LDA=postfix",
     help=ugettext_lazy("GID of the virtual user which owns domains/mailboxes/messages on the filesystem")
 )
 parameters.register_admin(
     "MAILBOX_TYPE", type="list", deflt="maildir",
     values=[("maildir", "maildir"), ("mbox", "mbox")],
+    visible_if="LDA=postfix",
     help=ugettext_lazy("Mailboxes storage format")
 )
 parameters.register_admin(
diff --git a/modoboa/admin/models.py b/modoboa/admin/models.py
index 07634b07d..f35c65b72 100644
--- a/modoboa/admin/models.py
+++ b/modoboa/admin/models.py
@@ -549,21 +549,21 @@ class Domain(DatesAware):
         return [oa.user for oa in self.owners.filter(user__is_superuser=False)]
         
     def create_dir(self):
-        if parameters.get_admin("CREATE_DIRECTORIES") == "yes":
+        if parameters.get_admin("LDA") == "postfix":
             path = "%s/%s" % (parameters.get_admin("STORAGE_PATH"), self.name)
             return exec_as_vuser("mkdir -p %s" % path)
         
         return True
 
     def rename_dir(self, oldname):
-        if parameters.get_admin("CREATE_DIRECTORIES") == "yes":
+        if parameters.get_admin("LDA") == "postfix":
             stpath = parameters.get_admin("STORAGE_PATH")
             return exec_as_vuser("mv %s/%s %s/%s" \
                                      % (stpath, oldname, stpath, self.name))
         return True
 
     def delete_dir(self):
-        if parameters.get_admin("CREATE_DIRECTORIES") == "yes":
+        if parameters.get_admin("LDA") == "postfix":
             return exec_as_vuser("rm -r %s/%s" \
                                      % (parameters.get_admin("STORAGE_PATH"), 
                                         self.name))
@@ -716,7 +716,7 @@ class Mailbox(DatesAware):
             self.path = "%s/Inbox" % self.address
         else:
             self.path = "%s/" % self.address
-        if parameters.get_admin("CREATE_DIRECTORIES") == "yes":
+        if parameters.get_admin("LDA") == "postfix":
             relpath = "%s/%s" % (self.domain.name, self.address)
             abspath = os.path.join(parameters.get_admin("STORAGE_PATH"), relpath)
             if os.path.exists(abspath):
@@ -736,7 +736,7 @@ class Mailbox(DatesAware):
         return True
 
     def rename_dir(self, newdomain, newaddress):
-        if parameters.get_admin("CREATE_DIRECTORIES") == "yes":
+        if parameters.get_admin("LDA") == "postfix":
             if self.domain.name == newdomain and newaddress == self.address:
                 return True
             oldpath = "%s/%s" % (parameters.get_admin("STORAGE_PATH"), self.domain.name)
@@ -753,7 +753,7 @@ class Mailbox(DatesAware):
         return True
 
     def delete_dir(self):
-        if parameters.get_admin("CREATE_DIRECTORIES") == "yes":
+        if parameters.get_admin("LDA") == "postfix":
             return exec_as_vuser("rm -r %s/%s/%s" \
                                      % (parameters.get_admin("STORAGE_PATH"),
                                         self.domain.name, self.address))
diff --git a/modoboa/lib/fixtures/demo.json b/modoboa/lib/fixtures/demo.json
index 96a4d9af4..87919d286 100644
--- a/modoboa/lib/fixtures/demo.json
+++ b/modoboa/lib/fixtures/demo.json
@@ -35,8 +35,8 @@
         "pk": 5,
         "model": "lib.parameter",
         "fields": {
-            "name": "admin.CREATE_DIRECTORIES",
-            "value": "yes"
+            "name": "admin.LDA",
+            "value": "dovecot"
         }
     },
     {
diff --git a/modoboa/static/js/twocols_nav.js b/modoboa/static/js/twocols_nav.js
index 4975fee1c..946159fce 100644
--- a/modoboa/static/js/twocols_nav.js
+++ b/modoboa/static/js/twocols_nav.js
@@ -47,15 +47,30 @@ TwocolsNav.prototype = {
         $('#' + this.options.divid + ' select').change();
     },
 
+    propagate_change: function($node) {
+        var $select = $node.find("select");
+        if ($select.length) {
+            $select.change();
+        }
+    },
+
     select_change: function(e) {
+        var instance = this;
         var $target = $(e.target);
+        var $parent = $target.parents("div.control-group");
 
         $('div[data-visibility-field="' + $target.attr("id") + '"]').each(function(idx) {
             var $this = $(this);
-            if ($this.attr("data-visibility-value") == $target.attr("value")) {
+
+            if ($parent.attr("disabled") === undefined && 
+                $this.attr("data-visibility-value") == $target.attr("value")) {
+                $this.attr("disabled", null);
                 $this.show();
+                instance.propagate_change($this)
             } else {
                 $this.hide();
+                $this.attr("disabled", "disabled");
+                instance.propagate_change($this);
             }
         });
     },