For the delivery attempts tuning, you can modify the following parameters in /opt/trend/imss/postfix/etc/postfix/main.cf:

queue_run_delay = 900s
minimal_backoff_time = 900s
maximal_backoff_time = 3600s
maximal_queue_lifetime = 1d

Whenever you make a change in the main.cf or master.cf file, execute the following command as root in order to refresh a running mail system:

# postfix reload

For more information on the parameters, refer to the following Postfix topic: Tuning the frequency of deferred mail delivery attempts.