diff --git a/addons/mail/mail_followers.py b/addons/mail/mail_followers.py
index 7406108229a..375ed9243a7 100644
--- a/addons/mail/mail_followers.py
+++ b/addons/mail/mail_followers.py
@@ -160,7 +160,7 @@ class mail_notification(osv.Model):
             pass
             # print quote_context
             # body_html = tools.append_content_to_html(body_html, quote_context, plaintext=False)
-        signature = msg.author_id and msg.author_id.user_ids[0].signature or ''
+        signature = msg.author_id and msg.author_id.user_id and msg.author_id.user_ids[0].signature or ''
         if signature:
             body_html = tools.append_content_to_html(body_html, tools.text2html(signature), plaintext=False)
 
diff --git a/addons/mail/mail_message.py b/addons/mail/mail_message.py
index 08c14dbc4d1..935350fdeb8 100644
--- a/addons/mail/mail_message.py
+++ b/addons/mail/mail_message.py
@@ -600,6 +600,8 @@ class mail_message(osv.Model):
     def create(self, cr, uid, values, context=None):
         if not values.get('message_id') and values.get('res_id') and values.get('model'):
             values['message_id'] = tools.generate_tracking_message_id('%(res_id)s-%(model)s' % values)
+        elif not values.get('message_id'):
+            values['message_id'] = tools.generate_tracking_message_id('private')
         newid = super(mail_message, self).create(cr, uid, values, context)
         self._notify(cr, SUPERUSER_ID, newid, context=context)
         return newid
diff --git a/addons/mail/mail_thread.py b/addons/mail/mail_thread.py
index b3e5423ae4d..1c27c6ce658 100644
--- a/addons/mail/mail_thread.py
+++ b/addons/mail/mail_thread.py
@@ -452,7 +452,7 @@ class mail_thread(osv.AbstractModel):
                     thread_id = model_pool.message_new(cr, user_id, msg, custom_values, context=context)
             else:
                 model_pool = self.pool.get('mail.thread')
-            model_pool.message_post_user_api(cr, uid, [thread_id], context=context, **msg)
+            model_pool.message_post_user_api(cr, uid, [thread_id], context=context, content_subtype='html', **msg)
         return thread_id
 
     def message_new(self, cr, uid, msg_dict, custom_values=None, context=None):