Changing the $from email in D6 contact_mail_user_submit() // Send the e-mail in the requested user language.
  drupal_mail('contact', 'user_mail', $to, user_preferred_language($account), $values, $**from**);


I wish to change the $from email to "do-not-reply@domain.com" to accommodate our email configuration.

$from is defined as $user-&gt;mail [here in the function][1] and I can't figure out how to override this via MODULE_form_contact_mail_user_alter.
You can implement hook_mail_alter() to do that, e.g.:

function MYMODULE_mail_alter(&amp;$message) {
  if ($message['id'] == 'contact_user_mail') {
    $message['from'] = 'do-not-reply@domain.com';
  }
}