Set up Accounting

The accounting and quota checks should be implemented in postfix smtpd_end_of_data_restrictions. If you're already using mtpolicyd for other check it may be necessary to setup a second virtual host for the accounting/quota configuration. Otherwise you can use the default port 12345 virual host.

Setup a second virtual host

First tell mtpolicyd to also listen on an addition port. In the global configuration add the new port to the port option:

  port="127.0.0.1:12345,127.0.0.1:12346"

Then add a new virtual host at the end of the configuration file:

  <VirtualHost 12346>
    name="accounting"
    # TODO: add plugins...
  </VirtualHost>

Configure the Accounting plugin

Now add the Accounting plugin to your virtual host:

  <Plugin AcctIP>
    module = "Accounting"
    fields = "client_address"
    # time_pattern = "%Y-%m"
    # table_prefix = "acct_"
  </Plugin>

And the restart mtpolicyd to reload the configuration.

The plugin will create a table for every field listed in "fields". By default the table prefix is acct_ so the table name will be acct_client_address in our example. The plugin will create a row within this table for every client_address and expanded time_pattern:

  mysql> select * from acct_client_address;
  +----+-------------------+---------+-------+------------+---------+-----------+
  | id | key               | time    | count | count_rcpt | size    | size_rcpt |
  +----+-------------------+---------+-------+------------+---------+-----------+
  |  1 | 2604:8d00:0:1::3  | 2015-01 |    18 |         18 |   95559 |     95559 |
  |  2 | 2604:8d00:0:1::4  | 2015-01 |    21 |         21 |   99818 |     99818 |
  ...
  +----+-------------------+---------+-------+------------+---------+-----------+

Activate the check in postfix

To active the check add the policyd to your smtpd_end_of_data_restrictions in main.cf:

  smtpd_end_of_data_restrictions = check_policy_service inet:127.0.0.1:12346

If you have multiple smtpd process configured in a smtp-filter setup make sure only one smtpd is doing accounting/quota checks. Deactivate the restrictions by adding the following option the the re-inject smtpd processes in master.cf:

  -o smtpd_end_of_data_restrictions=

Setup quota limits

To limit the number of messages a client_address is allowed to send add the following Quota plugin to your virtual host configuration before the Accounting plugin:

  <Plugin QuotaIP>
    module = "Quota"
    field = "client_address"
    metric = "count"
    threshold = 1000
    action = "defer you exceeded your monthly limit, please insert coin"
    # time_pattern = "%Y-%m"
    # table_prefix = "acct_"
  </Plugin>

Using per client_address quota limits

Create the following table structure in your MySQL database:

  CREATE TABLE `relay_policies` (
    `id` int(11) NOT NULL auto_increment,
    `desc` VARCHAR(64) NOT NULL,
    `config` TEXT NOT NULL,
    PRIMARY KEY  (`id`)
  ) ENGINE=InnoDB;
  INSERT INTO relay_policies VALUES(1, 'standard relay host', '{"quota_count":"10000"}');
  INSERT INTO relay_policies VALUES(2, 'premium relay host', '{"quota_count":"100000"}');
  CREATE TABLE `relay_hosts` (
    `id` int(11) NOT NULL auto_increment,
    `client_address` VARCHAR(64) NOT NULL,
    `relay_policy` int(11) NOT NULL,
    PRIMARY KEY  (`id`),
    KEY `relay_policy` (`relay_policy`),
    CONSTRAINT `relay_hosts_ibfk_1` FOREIGN KEY (`relay_policy`) REFERENCES `relay_policies` (`id`)
  ) ENGINE=InnoDB;
  INSERT INTO relay_hosts VALUES(NULL, '2604:8d00:0:1::3', 1);
  INSERT INTO relay_hosts VALUES(NULL, '2604:8d00:0:1::4', 2);

You can use the following SELECT statement to retrieve the configuration for a relay_host:

  mysql> SELECT p.config FROM relay_policies p JOIN relay_hosts h ON (h.relay_policy = p.id) WHERE h.client_address = '2604:8d00:0:1::4';
  +--------------------------+
  | config                   |
  +--------------------------+
  | {"quota_count":"100000"} |
  +--------------------------+
  1 row in set (0.00 sec)

To load the (JSON) configuration into the mtpolicyd session variables use the SqlUserConfig plugin and this SQL statement:

  <Plugin QuotaPolicyConfig>
    module = "SqlUserConfig"
    sql_query = "SELECT p.config FROM relay_policies p JOIN relay_hosts h ON (h.relay_policy = p.id) WHERE h.client_address=?"
    field = "client_address"
  </Plugin>

This plugin must be added before your Accounting and Quota plugins.

To use the quota_count value instead of the default threshold adjust your Quota plugin configuration:

  <Plugin QuotaIP>
    module = "Quota"
    field = "client_address"
    metric = "count"
    threshold = 1000
    uc_threshold = "quota_count"
    action = "defer you exceeded your monthly limit, please insert coin"
    # time_pattern = "%Y-%m"
    # table_prefix = "acct_"
  </Plugin>

If the session variable quota_count is defined it will be used as threshold instead of the value configured in mtpolicyd.conf.