How to flush the postfix queue

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: Function split() is deprecated in /var/www/info/drupal/modules/filter/filter.module on line 888.
: Function split() is deprecated in /var/www/info/drupal/modules/filter/filter.module on line 888.
: Function split() is deprecated in /var/www/info/drupal/modules/filter/filter.module on line 888.

For some reason Postfix sometimes get stuck.
To see if there are some email stuck in the queue you can simply type:

oktober# mailq
-Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient-------
38A1BF3B1*     1152 Thu Feb 12 00:22:39  www-data@oktober.momeunier.fr
                                         momeunier@gmail.com

-- 1 Kbytes in 1 Request.

Fortunately there is a little binary called postqueue that can help.