The identity ID is returned but not recorded in the table

Question

I am building a project in Zand 1.1.

I created 'email' table and I want to enter record with the insert method. My code looks like:

$this->_db_table = new Mconsole_Model_DbTable_Emailmessages(array(
   'db' => parent::getDb()
));
$this->_db_table->insert('email',data);

This code return last inserted id(for example '17') but no realy record inserted in the table. Can anyone help me?