This kind of problems occur because of a time-out setting on your server. If your delivery is stopping after a while such as after sending 5,000 emails or after 5 minutes, please check the following;
  • max_execution_time value in your PHP.INI is set to a very high number such as 7200 seconds (2 hours)
  • memory_limit in your PHP.INI is set to 256M and higher
  • Be sure that no other process execution time or memory allocation time limit is applied to your server
  • Be sure that your hosting company doesn't limit the number of emails outgoing from your server