Hi all, I have a mailman server with postfix. If I send many e-mails at the same time, I have a high number of re-delivery attempts because initially connections time out. I am playing with some parameters in main.cf but haven't been very successful yet. At the moment my main.cf says: smtp_destination_rate_delay = 120s smtp_destination_concurrency_limit = 1 initial_destination_concurrency = 1 default_process_limit = 5 A delayed delivery is acceptable so I just try to slow down to avoid timeouts. http://www.postfix.org/QSHAPE_README.html says: "When a host with lots of deferred mail is down for some time, it is possible for the entire deferred queue to reach its retry time simultaneously. This can lead to a very full active queue once the host comes back up. The phenomenon can repeat approximately every maximal_backoff_time seconds if the messages are again deferred after a brief burst of congestion. Perhaps, a future Postfix release will add a random offset to the retry time (or use a combination of strategies) to reduce the odds of repeated complete deferred queue flushes." I guess this feature would help.. Anyway, do you any more ideas how to improve the delivery? BTW: The server is in the Amazon EC2 cloud but I don't think it matters. Still, if I try a telnet on port 25, the connection opens faster from my office (ADSL) than from the Amazon VM. Thanks for all ideas Peter P.S. I am fiddling with it for so long, I typed luv-main.cf first;-)