I'm developing component and I wish to understand how to validate email value joined by user using joomla 1.7?

JHTML::_('behavior.formvalidation') without using this method.

Do this,

function validate()
{
    jimport('joomla.mail.helper');

    $valid = true;

     if ($this->_data->email && !JMailHelper::isEmailAddress($this->_data->email))
    {           
         $this->_app->enqueueMessage(JText::_('Invalid Email Address'),'error');                       
         $valid = false;           
    }   
    return $valid; 
}