Study the following thoroughly... not a subquery in sight...
 DROP TABLE IF EXISTS my_table;
 CREATE TABLE my_table
 (rownum INT NOT NULL AUTO_INCREMENT PRIMARY KEY
 ,my_column INT NOT NULL
 ,next_retry_time DATETIME NOT NULL
 ,destaddr VARCHAR(20) NOT NULL
 );
 INSERT INTO my_table (my_column,next_retry_time,destaddr)
 VALUES
 (101,NOW(),'my_string'),
 (102,NOW(),'not_my_string'),
 (101,NOW(),'not_my_string'),
 (102,NOW(),'not_my_string'),
 (102,NOW(),'my_string'),
 (103,NOW(),'my_string');
 SELECT * FROM my_table;
 +--------+-----------+---------------------+---------------+
 | rownum | my_column | next_retry_time     | destaddr      |
 +--------+-----------+---------------------+---------------+
 |      1 |       101 | 2013-04-04 12:50:51 | my_string     |
 |      2 |       102 | 2013-04-04 12:50:51 | not_my_string |
 |      3 |       101 | 2013-04-04 12:50:51 | not_my_string |
 |      4 |       102 | 2013-04-04 12:50:51 | not_my_string |
 |      5 |       102 | 2013-04-04 12:50:51 | my_string     |
 |      6 |       103 | 2013-04-04 12:50:51 | my_string     |
 +--------+-----------+---------------------+---------------+
 SELECT *
   FROM my_table x
   JOIN my_table y
     ON y.my_column = x.my_column
  WHERE y.destaddr = 'my_string'
    AND y.rownum < 3;
 +--------+-----------+---------------------+---------------+--------+-----------+---------------------+-----------+
 | rownum | my_column | next_retry_time     | destaddr      | rownum | my_column | next_retry_time     | destaddr  |
 +--------+-----------+---------------------+---------------+--------+-----------+---------------------+-----------+
 |      1 |       101 | 2013-04-04 12:50:51 | my_string     |      1 |       101 | 2013-04-04 12:50:51 | my_string |
 |      3 |       101 | 2013-04-04 12:50:51 | not_my_string |      1 |       101 | 2013-04-04 12:50:51 | my_string |
 +--------+-----------+---------------------+---------------+--------+-----------+---------------------+-----------+
 UPDATE my_table x
   JOIN my_table y
     ON y.my_column = x.my_column
    SET x.next_retry_time = NOW()
  WHERE y.destaddr = 'my_string'
    AND y.rownum < 3;
 SELECT * FROM my_table;
 +--------+-----------+---------------------+---------------+
 | rownum | my_column | next_retry_time     | destaddr      |
 +--------+-----------+---------------------+---------------+
 |      1 |       101 | 2013-04-04 12:52:28 | my_string     |
 |      2 |       102 | 2013-04-04 12:50:51 | not_my_string |
 |      3 |       101 | 2013-04-04 12:52:28 | not_my_string |
 |      4 |       102 | 2013-04-04 12:50:51 | not_my_string |
 |      5 |       102 | 2013-04-04 12:50:51 | my_string     |
 |      6 |       103 | 2013-04-04 12:50:51 | my_string     |
 +--------+-----------+---------------------+---------------+