[patrickb]

I'm posting this here in case anybody else needs it in the future.

I basically used the mail_send hook to check the subject. If it matches the one for the lost password recovery, I display an error message.

It might not be the best way to do it, but it works.

PHP Code:

if( $fromemail == $vbulletin->options['webmasteremail'] )
{    
    foreach ($vbulletin->languagecache as $language)
    {
        eval('$' . 'lostsubject = "' . fetch_phrase('lostpw', 'emailsubject', 'emailsubject_', true, true, $language['languageid'], false) . '";' );
        if( $subject == $lostsubject )
        {
            eval(standard_error(fetch_error('password_update_disabled')));
        }
    }
}