Admin panel:

Only invited user can register in strict mode,
Set mail server in admin panel,
Switch strict mode in admin panel,
Invite people to system in admin panel

client/components/settings/settingBody.styl

@@ -0,0 +1,112 @@
+.flex
+  display: -webkit-box
+  display: -moz-box
+  display: -webkit-flex
+  display: -moz-flex
+  display: -ms-flexbox
+  display: flex
+
+.setting-content
+  padding 30px
+  color: #727479
+  background: #dedede
+  width 100%
+  height 100%
+  position: absolute;
+
+  .content-title
+    font-size 20px
+
+  .content-body
+    display flex
+    padding-top 15px
+    height 100%
+
+    .side-menu
+      background-color: #f7f7f7;
+      border: 1px solid #f0f0f0;
+      border-radius: 4px;
+      width: 250px;
+      box-shadow: inset -1px -1px 3px rgba(0,0,0,.05);
+
+      ul
+
+        li
+          margin: 0.1rem 0.2rem;
+
+          &.active
+            background #fff
+            box-shadow 0 1px 2px rgba(0,0,0,0.15);
+
+          &:hover
+            background #fff
+            box-shadow 0 1px 2px rgba(0,0,0,0.15);
+          a
+            @extends .flex
+            padding: 1rem 0 1rem 1rem
+            width: 100% - 5rem
+
+
+            span
+              font-size: 13px
+
+    .main-body
+      padding: 0.1em 1em
+
+      ul
+        li
+          padding: 0.5rem 0.5rem;
+
+          a
+            .is-checked
+              border-bottom: 2px solid #2980b9;
+              border-right: 2px solid #2980b9;
+              
+            span 
+              padding: 0 0.5rem
+              
+          .invite-people
+            padding-left 20px;
+            li
+              min-width: 500px;
+
+              ul.no-margin-bottom
+                margin-bottom: 0;
+
+              .bg-white
+                a
+                  background  #f7f7f7
+                  &.is-checked
+                    background #fff
+
+
+.option
+  @extends .flex
+  -webkit-border-radius: 3px;
+  border-radius: 3px;
+  background: #fff;
+  text-decoration: none;
+  -webkit-box-shadow: 0 1px 2px rgba(0,0,0,0.2);
+  box-shadow: 0 1px 2px rgba(0,0,0,0.2);
+  margin-top: 5px;
+  padding: 5px;
+
+.title
+  font-weight 700;
+  margin-bottom 0.5rem;
+.description
+  margin-bottom 0.5rem;
+.bg-white
+  background #f9fbfc;
+
+.form-control.has-error
+  border-color: #a94442;
+  box-shadow: inset 0 1px 1px rgba(0,0,0,.075);
+
+li.has-error
+  color #a94442
+  .form-group
+    .form-control
+      border-color: #a94442;
+      box-shadow: inset 0 1px 1px rgba(0,0,0,.075);
+