last_poll isn't set
Polling runs every time of cron.php run, because last_poll isn't set.
mysql> mysql> select * from getmail;
+---------------+---------+--------+--------+------+-------------+-----------+------+-------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----+--------+----------+------+---------------------+
| id | user_id | name | active | type | server | mailboxes | port | user | pass | ssl | delete | read_all | poll | last_poll |
+---------------+---------+--------+--------+------+-------------+-----------+------+-------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----+--------+----------+------+---------------------+
| 53fdf17ef26c6 | 127 | web.de | 1 | POP3 | pop3.web.de | NULL | 995 | xyz | abc123 | 1 | 1 | 1 | 1800 | 0000-00-00 00:00:00 |
+---------------+---------+--------+--------+------+-------------+-----------+------+-------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----+--------+----------+------+---------------------+
Maybe this is a problem with the access rights of cron.php?