Alter Webform outgoing e-mail

gistfile1.php

<?php
/**
 * Implements hook_mail_alter().
 */
function mymodule_mail_alter(&$message) {
  if ($message['id'] == 'webform_submission') {
    // Use the From header as a Reply-to and set the From header to the site
    // mail address. Trying to say e-mail is "From" other domains will get the
    // mail marked as spam, so instead the e-mail is always from webform.com,
    // but the reply address is the user-specified address.
    $message['headers']['Reply-to'] = $message['from'];
    // This first header is apparently not used, update for consistency.
    $message['headers']['From'] = $message['headers']['Sender'];
    // The From address actually used in the sent mail.
    $message['from'] = $message['headers']['Sender'];

    // Users prefer to have their own (as set in the "Reply-to" header) show up
    // in the "From" address, even if the address is going to be @webform.com.
    // Pull out the name from the Reply-to header and use it on From.
    $replyto_parts = array();
    $from_parts = array();
    $email_regex = '/^"(.+?)"[ ]+<(.*?)>$/';

    // We can only update the "From" name if a name is actually given.
    if (preg_match($email_regex, $message['headers']['Reply-to'], $replyto_parts)) {
      // Update "From" addresses that are "Name" <email@domain.com>
      if (preg_match($email_regex, $message['from'], $from_parts)) {
        $message['from'] = $replyto_parts[1] . ' <' . $from_parts[2] . '>';
      }
      // Update "From" addresses that are just the e-mail (more common).
      elseif (valid_email_address($message['from'])) {
        $message['from'] = $replyto_parts[1] . ' <' . $message['from'] . '>';
      }
    }
  }
}