Several parameters of frequency control for postfix letters

Postfix a few of the frequency control letters:

Smtpd_client_connection_rate_limit=5

The frequency control of the IP address connection.

Smtpd_client_message_rate_limit=5

The frequency control that the client sends the message. (In some cases the effect of smtpd_client_message_rate_limit and Smtpd_client_connection_rate_limit is the same. Smtpd_client_connection_rate_ Limit is when you connect to server port 25 to start the calculation, smtpd_client_message_rate_limit when you send the message.

smtpd_client_recipient_rate_limit=10

RCPT to frequency control, that is to how many individuals.

Smtpd_client_event_limit_exceptions = ${smtpd_client_connection_limit_exceptions: $mynetworks}

Refers to the network that does not do frequency control detection, the default is Mynetworks.

Performance control of Posftfix

The postfix performance is controlled in order to ensure that postfix can function properly when the mail storm is encountered. In general, we can adjust the performance of Postfix by configuring the following postfix parameters, which are configured by the MAIL.CF configuration file, and do not forget to run the postfix reload command to make the configuration effective after modification.

1. Number of processes limit

You can control the maximum number of processes that the postfix system can run at the same time by Default_process_limit parameters. The default value is 50.

2. Concurrent connection restrictions on the same target host

When an SMTP connection is made to the same target host, Postfix initiates two SMTP connections and, if successful, increases the number of concurrent SMTP connections and reduces the number of concurrent connections when congestion is encountered. The concurrent connections of the same target host are controlled by the following parameters in Postfix:

* Initial_destination_concurrency: Controls the number of simultaneous initialization concurrent connections to the same target host. The default value is 2.

* Default_destination_concurrency_limit: Controls the maximum number of concurrent connections to the same target host after an initialization connection. The default value is 10.

* Local_destination_concurrency_limit: Controls the maximum number of simultaneous messages delivered to the same local recipient. The default value is 2, because the delivery work can only be performed one at a time on the local same recipient, so it is useless to set it up in large.

3. Limit the number of recipients to the same message

The Default_destination_recipient_limit parameter is used to control the delivery agent for the postfix, such as

SMTP process) can send the same message to many recipients. The default value is 50. You can also override the default by explicitly pointing to the drop agent's parameters. If you use Smtpd_recipient_limit to specify how many recipients the SMTP delivery agent can send the same message to, the default value for this parameter is 1000.

4. Deferred post control

With the Defer_transports parameter, we can postpone the delivery of the message specified by this parameter until Postfix explicitly put forward the delivery request. Let's take a look at the following example:

There is a small local area network where users send mail to a postfix inside the LAN

mail server, and then send the message by dialing on the server. At this point we can specify the value of this parameter:

Defer_transports = SMTP

This statement indicates that Postfix deferred posting all the messages until the SENDMAIL-Q command was executed, so

We can add sendmail-q to the PPP script to let Postfix start posting the message after the dial-up success.

5. On post-delivery control for deferred mail

Re-posting control of deferred messages can be achieved by several of the following parameters:

Queue_run_delay: Sets the frequency at which queue management scans deferred message queues, with a default value of 1000 seconds.

Maximal_queue_lifetime: sets Postfix to delay the message and then deferred the lifetime of the message queue before it returns undeliverable information when the post is discarded.

Minimal_backoff_time: When a mail delivery fails, the message queue ignores the existence of the message for a period of time, which is the time stamp we talked about earlier. This parameter is used to set the minimum time stamp. The default value is 1000 seconds.

Maximal_backoff_time: Set the maximum time stamp.