select mid, stamp, message, count(message) as count, type, title from bm_message_queue where sent = 1 and mid >'0'  group by mid order by stamp

Explain:
1, 'SIMPLE', 'bm_message_queue', 'ref', 'mid_index,sent', 'sent', '1', 'const', 113835, 'Using where; Using temporary; Using filesort'

DROP TABLE IF EXISTS `pollobm2`.`bm_message_queue`;
CREATE TABLE  `pollobm2`.`bm_message_queue` (
  `id` int(10) unsigned NOT NULL auto_increment,
  `stamp` timestamp NOT NULL default CURRENT_TIMESTAMP,
  `phone` varchar(10) default NULL,
  `message` text,
  `sent` tinyint(3) unsigned NOT NULL default '0',
  `cid` int(10) unsigned default NULL,
  `mid` int(10) unsigned default NULL,
  `title` varchar(85) default NULL,
  `type` varchar(10) default NULL,
  `email` varchar(85) default NULL,
  `opened` varchar(3) NOT NULL default 'No',
  `open_time` datetime default NULL,
  `ip_address` varchar(32) default NULL,
  `status` varchar(20) default NULL,
  `refId` int(10) unsigned NOT NULL default '0',
  PRIMARY KEY  (`id`),
  UNIQUE KEY `unique_msg_ind` (`phone`,`mid`),
  KEY `phone_ind` (`phone`),
  KEY `mid_index` (`mid`),
  KEY `sent` (`sent`),
  KEY `email_ind` (`email`)
) ENGINE=InnoDB AUTO_INCREMENT=290205 DEFAULT CHARSET=utf8 ROW_FORMAT=DYNAMIC;