Simpletest for Sending Mail
You need three functions.

1) module_submit.
2) Create a function to send the mail.
3) create hook_mail.

a complete example: file sendmailtest.info

name = sendmailtest
description = sendmailtest
core = 7.x


file sendmailtest.module

&lt;?php

function sendmailtest_menu() {
 $items['sendmailtest'] = array(
   'title' =&gt; 'send mail test',
   'page callback' =&gt; 'drupal_get_form',
   'page arguments' =&gt; array('sendmailtest'),
   'access callback' =&gt; TRUE
 );
 return $items;
}


function sendmailtest($form, &amp;$form_state){


 $form['submit'] = array(
  '#value' =&gt; 'Send Mail Test',
  '#type' =&gt; 'submit',
 );
 //Fundamental devolver el objeto-array form
 return $form;
}

function sendmailtest_submit($form, &amp;$form_state){

 drupal_set_message('Test ok');

 sendmailtest_send($form_state['values']);

}

function sendmailtest_send($form_values) {
  // All system mails need to specify the module and template key (mirrored from
  // hook_mail()) that the message they want to send comes from.
  $module = 'sendmailtest';
  $key = 'sendmailtest';

  // Specify 'to' and 'from' addresses.
  //$to = $form_values['email'];
  $to = 'jeremiselxi@gmail.com';
  $from = variable_get('site_mail', 'admin@example.com');

  // "params" loads in additional context for email content completion in
  // hook_mail(). In this case, we want to pass in the values the user entered
  // into the form, which include the message body in $form_values['message'].
  $params = $form_values;

  // The language of the e-mail. This will one of three values:
  // - user_preferred_language(): Used for sending mail to a particular website
  //   user, so that the mail appears in their preferred language.
  // - global $language: Used when sending a mail back to the user currently
  //   viewing the site. This will send it in the language they're currently
  //   using.
  // - language_default(): Used when sending mail to a pre-existing, 'neutral'
  //   address, such as the system e-mail address, or when you're unsure of the
  //   language preferences of the intended recipient.
  //
  // Since in our case, we are sending a message to a random e-mail address that
  // is not necessarily tied to a user account, we will use the site's default
  // language.
  $language = language_default();

  // Whether or not to automatically send the mail when drupal_mail() is
  // called. This defaults to TRUE, and is normally what you want unless you
  // need to do additional processing before drupal_mail_send() is called.
  $send = TRUE;
  // Send the mail, and check for success. Note that this does not guarantee
  // message delivery; only that there were no PHP-related issues encountered
  // while sending.
  $result = drupal_mail($module, $key, $to, $language, $params, $from, $send);
  if ($result['result'] == TRUE) {
    drupal_set_message(t('Your message has been sent.'));
  }
  else {
    drupal_set_message(t('There was a problem sending your message and it was not sent.'), 'error');
  }

}


function sendmailtest_mail($key, &amp;$message, $params) {
  switch ($key) {
    // Send a simple message from the contact form.
    case 'sendmailtest':


      $message['subject'] = 'Test subject';

      $body= 'Test Body';
      $message['body'][] = check_plain($body);
      break;
  }
}