Postfix timeout for unsent emails

Question

I am using Postfix for send about 20 000 – 30 000 e-mail per day. For messages not ended into a spam, the script is running with 1 second break every email send. As a result, e-mail are sending about 5 - 8 hours.

When an error occurs on the server (for example network goes down), script is still running and Postfix queues emails. When network connection come back, Postfix try to send unsent e-mail at once, about 30 emals per second.

Is there any parameter for Postfix which would allow for a slowdown sending queues e-mails?

Answer 1

There are a lot of options which allow fine tuning of the queues, but a lot depends on where these mails are being sent to.

Some options, like default_destination_concurrency_limit which defaults to 20, will count when the email is being sent to a single destination. The queue_run_delay is the time the server takes before rescanning the deferred directory for resend attempts, and adjusting the minimal_backof_time and maximal_backoff_time (the time postfix waits before retrying) to be longer, could also slow how many emails the server tries to send when the network is back.

You do need to be careful, as a lot of these values are set up to keep the queues from becoming too full, if there are issues. The postfix site has some very good documentation on the subject.