How to send emails in Drupal programmatically

drupal_mail('system', 'mail', 'yourmail@gmail.com', language_default(), array(
  'context' => array(
    'subject' => 'Awesome subject',
    'message' => 'Email body message here',
  )
));

/**
 * Implements hook_mail().
 */
function yourmodule_mail($key, &$message, $params) {
  if ($key == 'my_example') {
    $message['subject'] = 'Email subject';
    $message['body'][] = "This is a email message \n Some variable = {$params['some_var']}";
  }
}

drupal_mail('yourmodule', 'my_example', 'to-user@mail.com',
language_default(), array('some_var' => 'Some value'));