Miscellany

+----+-------------+-------+-------+---------------+------+---------+------+--------+-------------+
| id | select_type | table | type  | possible_keys | key  | key_len | ref  | rows   | Extra       |
+----+-------------+-------+-------+---------------+------+---------+------+--------+-------------+
|  1 | SIMPLE      | smtp  | range | dttm          | dttm | 8       | NULL | 705218 | Using where |
+----+-------------+-------+-------+---------------+------+---------+------+--------+-------------+