For anyone wishing to use a server cron job instead of depending on the pseudo one provided by WordPress, the alo-easymail instructions suggest you need to configure a server cron job like this:
*/5 * * * * GET http://yourwebsite.com/wp-cron.php?doing_wp_cron > /dev/null
Maybe that works on some servers, on my server I needed to do this instead:
*/5 * * * * wget -q "http://yourwebsite.com/wp-cron.php?doing_wp_cron"
Also, don't forget to add this to wp-config.php
... to disable the default WordPress cron manager so there won't be any conflict with the server cron job.