Postfix is a MTA which is rich in features and if configured properly can be used for sending mails faster than other MTA’s. Postfix is mainly preferred by admins when it comes for bulk mailing. There are different ways in which we can configure mail server for bulk mailing.
But if the list if quite large, we may need to do some tweaks in the conf to handle the additional overhead. All these values should be changed gradually keeping the server hardware configuration and your requirements in your mind.
Some of the values which will help are given below.
1. Increase the number of SMTP process, increase the value “default_process_limit” in main.cf
default_process_limit = 75
2. in_flow_delay – Adjust interval for accepting new messages, when the message arrival rate exceeds the message delivery rate. With the default 50 Postfix SMTP server process limit, value 1s limits the mail inflow to 50 messages per second above the number of messages delivered per second.
3. Another value which help is increasing speed is default_destination_concurrency_limit parameter . Default value is 10 .This controls how many messages may be sent to the same destination simultaneously. We can increase this safely between 20 – 40 according to the server capacity.
default_destination_concurrency_limit = 30