mail.php

<?php

/**
 * Implements hook_form().
 */
function contact_form($form, &$form_state) {

  $form['email'] = array(
    '#type' => 'textfield',
    '#required' => TRUE,
    '#title' => t('Email'),
    '#title_display' => 'invisible',
    '#attributes' => array ('placeholder' => t('Email')),
  );

   $form['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Submit'),
    '#submit' => array('contact_form_submit'),
  );

  $form['#validate'] = array('contact_form_validate');

  return $form;
}

/**
 * Implements hook_validate().
 */
function contact_form_validate($form, &$form_state) {

  $email = $form_state['values']['email'];

  if(valid_email_address($email) == 0) {
    form_set_error('email', t('Not a valid email address'));
  }
}

/**
 * Submit handler.
 * @param $form
 * @param $form_state
 */
function contact_form_submit($form, &$form_state) {

  $mail_message = t("Foo");
  $to = '[email protected]';
  $email = $form_state['values']['email'];
  $send = TRUE;



  $key = 'contact_form_email';
  $from = $form_state['values']['email'];

  $message = drupal_mail('contact_form', 'notify', $email, language_default());

  if ($message['result'] == TRUE) {
    drupal_set_message($mail_message,'status');
  }
  else {
    drupal_set_message(t('There was a problem sending your message and it was not sent.'), 'error');
  }

}

/**
 * Builds email message.
 * @param $form_state
 * @return $body
 */
function get_mail_content($form_state) {

  $content = array();
  $body = '<b>' . 'Email: ' . '</b>' . ' ' . $form_state['values']['email'];
  $content['body'] = $body;
  return $content;

}

/**
 * Implements hook_mail().
 */
function contact_form_mail($key, &$message, $params) {

  $language = $message['language'];

  switch ($key) {
    case 'contact_form_email':
      $message['headers']['Content-Type'] = 'text/html; charset=UTF-8;';
      $message['subject'] = t('YO');
      $message['email'][] = $params['email'];
      break;
  }

}