diff --git a/extensions/webmail/forms.py b/extensions/webmail/forms.py
index 8e5b75abc..5bab1fc0b 100644
--- a/extensions/webmail/forms.py
+++ b/extensions/webmail/forms.py
@@ -5,7 +5,7 @@ class ComposeMailForm(forms.Form):
     from_ = forms.CharField(label=_("From"))
     to = forms.CharField(label=_("To"), widget=forms.Textarea())
     cc = forms.CharField(label=_("Cc"), widget=forms.Textarea(), required=False)
-    subject = forms.CharField(label=_("Subject"), max_length=255)
+    subject = forms.CharField(label=_("Subject"), max_length=255, required=False)
 
 class FolderForm(forms.Form):
     name = forms.CharField()
diff --git a/extensions/webmail/lib.py b/extensions/webmail/lib.py
index c00a611a7..819736592 100644
--- a/extensions/webmail/lib.py
+++ b/extensions/webmail/lib.py
@@ -542,7 +542,7 @@ def send_mail(request, origmsg=None, posturl=None):
     """
     from email.mime.multipart import MIMEMultipart
     from forms import ComposeMailForm
-    from modoboa.lib.webutils import getctx, ajax_simple_response
+    from modoboa.lib.webutils import getctx, ajax_simple_response, _render_to_string
     from modoboa.auth.lib import get_password
 
     form = ComposeMailForm(request.POST)
@@ -623,13 +623,13 @@ def send_mail(request, origmsg=None, posturl=None):
         del request.session["compose_mail"]
         return True, ajax_simple_response(getctx("ok", url=get_current_url(request)))
 
-
-    listing = render_to_string("webmail/compose.html", 
-                               {"form" : form, 
+    listing = _render_to_string(request, "webmail/compose.html", 
+                               {"form" : form, "noerrors" : True,
                                 "body" : request.POST["id_body"].strip(),
                                 "posturl" : posturl})
+    error = _("Red fields are mandatories")
     return False, ajax_simple_response(
-        getctx("ko", level=2, listing=listing, editor=editormode)
+        getctx("ko", level=2, respmsg=error, listing=listing, editor=editormode)
         )
 
 class AttachmentUploadHandler(FileUploadHandler):
diff --git a/extensions/webmail/static/js/webmail.js b/extensions/webmail/static/js/webmail.js
index 7072210e3..32cdec3c5 100644
--- a/extensions/webmail/static/js/webmail.js
+++ b/extensions/webmail/static/js/webmail.js
@@ -762,6 +762,8 @@ function sendmail_callback(evt) {
                 current_anchor.get_callback("compose")(resp);
                 if ($defined(resp.respmsg)) {
                     infobox.error(resp.respmsg);
+                } else {
+                    infobox.hide();
                 }
                 enable_link(this, sendmail_callback);
                 return;
diff --git a/static/css/default.css b/static/css/default.css
index b78bf88a1..3e0f0a58d 100644
--- a/static/css/default.css
+++ b/static/css/default.css
@@ -403,6 +403,11 @@ div.row label {
     padding: 3px 0;
 }
 
+.missing input,
+.missing textarea { 
+    background-color: #F9D2D2;
+}
+
 .error {
     margin: 0 auto;
     padding: 5px;
diff --git a/templates/common/genericform.html b/templates/common/genericform.html
index 76adb06ff..13e60edf2 100644
--- a/templates/common/genericform.html
+++ b/templates/common/genericform.html
@@ -7,6 +7,6 @@
     <div class="tip-text">{% trans field.help_text %}</div>
   </div>
   {% endif %}
-  <label for="id_{{ field.html_name }}">{% trans field.label %}</label><div class="input_container clearfix"> {{ field }}</div> {% ifequal noerrors False %}{{ field.errors }}{% endifequal %}
+  <label for="id_{{ field.html_name }}">{% trans field.label %}</label><div class="input_container clearfix {% if field.errors %}missing{% endif %}"> {{ field }}</div> {% ifequal noerrors False %}{{ field.errors }}{% endifequal %}
 </div>
 {% endfor %}