Incorrect authentication data magento
<p>When I try to send email I got below error in exception log 
How I can fix this?  </p>

<blockquote>
  <p>2016-03-10T08:46:09+00:00 ERR (3): 
          exception 'Zend_Mail_Protocol_Exception' with message 'Incorrect authentication data
          ' in /home/cvbnm/public_html/lib/Zend/Mail/Protocol/Abstract.php:431
          Stack trace:
          #0 /home/cvbnm/public_html/lib/Zend/Mail/Protocol/Smtp/Auth/Login.php(95): Zend_Mail_Protocol_Abstract->_expect(235)
          #1 /home/cvbnm/public_html/lib/Zend/Mail/Protocol/Smtp.php(217): Zend_Mail_Protocol_Smtp_Auth_Login->auth()
          #2 /home/cvbnm/public_html/lib/Zend/Mail/Transport/Smtp.php(200): Zend_Mail_Protocol_Smtp->helo('localhost')
          #3 /home/cvbnm/public_html/lib/Zend/Mail/Transport/Abstract.php(348): Zend_Mail_Transport_Smtp->_sendMail()
          #4 /home/cvbnm/public_html/lib/Zend/Mail.php(1194): Zend_Mail_Transport_Abstract->send(Object(Zend_Mail))
          #5 /home/cvbnm/public_html/app/code/local/Mage/Core/Model/Email/Template.php(458): Zend_Mail->send(Object(Zend_Mail_Transport_Smtp))
          #6 /home/cvbnm/public_html/app/code/local/Mage/Core/Model/Email/Template.php(518): Mage_Core_Model_Email_Template->send('yuvrajkumbhar30...', NULL, Array)
          #7 /home/cvbnm/public_html/app/code/local/Mage/Contacts/controllers/IndexController.php(241): Mage_Core_Model_Email_Template->sendTransactional('1', 'general', 'yuvrajkumbhar30...', NULL, Array)
          #8 /home/cvbnm/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Contacts_IndexController->postAction()
          #9 /home/cvbnm/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('post')
          #10 /home/cvbnm/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
          #11 /home/cvbnm/public_html/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
          #12 /home/cvbnm/public_html/app/Mage.php(684): Mage_Core_Model_App->run(Array)
          #13 /home/cvbnm/public_html/index.php(84): Mage::run('', 'store')
          #14 {main}</p>
</blockquote>