send emails to specific addresses based on value of fields
I am a little confused about your question. But here is an example for you to send email using hook_mail. Hope you can get some idea from this:

/**
* Implement hook_mail() function
*/
function test_mail_node_mail($key, &amp;$message, $params) {
   $headers = array(
     'MIME-Version' =&gt; '1.0',
     'Content-Type' =&gt; 'text/html; charset=UTF-8; format=flowed; delsp=yes',
     'Content-Transfer-Encoding' =&gt; '8Bit',
     'X-Mailer' =&gt; 'Drupal'
   );

   foreach ($headers as $key =&gt; $value) {
      $message['headers'][$key] = $value;
   }

   $message['subject'] = $params['subject'];
   $message['body'] = $params['body'];
}

/**
* Implement hook_submit() function
*/
function test_mail_node_submit($node, $form, &amp;$form_state) {
   if($node-&gt;type == 'rso') {
     if ($node-&gt;field_b['und'][0]['value'] == TRUE){
       if ($node-&gt;field_a['und'][0]['tid'] == '10'){
          // mail('example1@mail.com', 'example2@mail.com', 'example text');
          $valid_email = array('example1@mail.com', 'example2@mail.com');
          $params = array(
             'body' =&gt; 'Your body text',
             'subject' =&gt; 'This is a subject',
          );
          drupal_mail('test_mail_node', 'HTML', $valid_email, 'en', $params));
       }
     }
  }
}