Test Drupal email. Edit and add to the Drupal docroot to see if you can send a message. Note that this will not hook phpmailer or other libs that may be in use. Mainly for a quick proof of life type of check.

drupal-email-test.php

<?php
// Replace <user>@<host>, place in a drupal docroot, hit it with a browser.
require_once './includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

$message = array(
  'id' => 'email_tester',
  'to' => '<user>@<host>',
  'subject' => t('Test subject'),
  'body' => t('This is a test message to fill in the body.'),
  'headers' => array('From' => '<user>@<host>'),
);

if (drupal_mail_send($message)) {
  print 'Message sent';
} else {
  print 'Message Failed';
}