Sending is very slow using "phpList cron job"

As the webmaster of a club i have to send around 400 e-mails once a month. I am using the latest version of phpList and “phpList cron job” (“secret for remote processing”). Initially, shipping took about 5 hours. The last shipment in April took 5 days! and with the current shipping became 45 in 15 hours! emails sent. Something is obviously wrong, but what? My config.php looks like this:

$default_system_language = “de”;
// what is your Mysql database server hostname
$database_host = ‘xxxxx’;
// what is the name of the database we are using
$database_name = ‘';
// what user has access to this database
$database_user = '
';
// and what is the password to login to control the database
$database_password = '
*******’;
// if you have an SMTP server, set it here. Otherwise it will use the normal php mail() function
//# if your SMTP server is called “smtp.mydomain.com” you enter this below like this:
//#
//# define(“PHPMAILERHOST”,‘smtp.mydomain.com’);
define(‘PHPMAILERHOST’, ‘lx7.hoststar.hosting’);
$phpmailer_smtpuser = ‘newsletter@computeria-solothurn.ch’;
$phpmailer_smtppassword = *********;
//#
//# you can set this to send out via a different SMTP port
define(‘PHPMAILERPORT’,465);
// to use SSL/TLS when sending set this value
// it can either be “ssl” or “tls” or false to not use SSL/TLS at all
define(“PHPMAILER_SECURE”,‘ssl’);
//#
// if TEST is set to 1 (not 0) it will not actually send ANY messages, but display what it would have sent
// this is here, to make sure you edited the config file and mails are not sent “accidentally”
// on unmanaged systems
define(‘TEST’, 0);

using attachments requires PHP 4.1.0 and up

define(‘ALLOW_ATTACHMENTS’,1);
//#
// define(‘MAILQUEUE_BATCH_SIZE’, 40);
// define(‘MAILQUEUE_BATCH_PERIOD’, 300);
/*

  • Settings for handling bounces
  • This section is OPTIONAL, and not necessary to send out mailings, but it is highly recommended to correctly
  • set up bounce processing. Without processing of bounces your system will end up sending large amounts of
  • unnecessary messages, which overloads your own server, the receiving servers and internet traffic as a whole

==============================================================================================================
*/
// Message envelope.
// This is the address that most bounces will be delivered to
// Your should make this an address that no PERSON reads
// but a mailbox that phpList can empty every so often, to process the bounces
$message_envelope = ‘bounces@computeria-solothurn.ch’;
// Handling bounces. Check README.bounces for more info
// This can be ‘pop’ or ‘mbox’
$bounce_protocol = ‘pop’;
// set this to 0, if you set up a cron to download bounces regularly by using the
// commandline option. If this is 0, users cannot run the page from the web
// frontend. Read README.commandline to find out how to set it up on the
// commandline
define(‘MANUALLY_PROCESS_BOUNCES’, 1);
// when the protocol is pop, specify these three
$bounce_mailbox_host = ‘lx7.hoststar.hosting’;
$bounce_mailbox_user = ‘bounces@computeria-solothurn.ch’;
$bounce_mailbox_password = ‘***********’;
// the “port” is the remote port of the connection to retrieve the emails
// the default should be fine but if it doesn’t work, you can try the second
// one. To do that, add a # before the first line and take off the one before the
// second line
//$bounce_mailbox_port = ‘110/pop3/notls’;
//$bounce_mailbox_port = “110/pop3”;
// it’s getting more common to have secure connections, in which case you probably want to use
//$bounce_mailbox_port = “995/pop3/ssl/novalidate-cert”;
$bounce_mailbox_port = “995/pop3/novalidate-cert”;
// when the protocol is mbox specify this one
// it needs to be a local file in mbox format, accessible to your webserver user
//$bounce_mailbox = ‘/var/mail/listbounces’;
// set this to 0 if you want to keep your messages in the mailbox. this is potentially
// a problem, because bounces will be counted multiple times, so only do this if you are
// testing things.
$bounce_mailbox_purge = 1;
// set this to 0 if you want to keep unprocessed messages in the mailbox. Unprocessed
// messages are messages that could not be matched with a user in the system
// messages are still downloaded into phpList, so it is safe to delete them from
// the mailbox and view them in phpList
$bounce_mailbox_purge_unprocessed = 1;
// how many bounces in a row need to have occurred for a user to be marked unconfirmed
$bounce_unsubscribe_threshold = 5;
// choose the hash method for password
// check the extended config for more info
// in most cases, it is fine to leave this as it is
define(‘HASH_ALGO’, ‘sha256’);