NAME

       ratefilter - Rate-limiting mail filter

SYNOPSIS

       filterctl {[start] | [stop]} ratefilter

DESCRIPTION

       Enable this filter to enforce a maximum number of messages accepted from the same sender.

       ratefilter uses the following configuration files. Changes to the following files do not
       take effect until the filter has been stopped and restarted.

       /etc/courier/filters/ratefilter-interval
           This file contains a single numerical value that sets the rate limiting time interval
           setting, in seconds. The default value is sixty seconds. Sixty seconds is also the
           minimum acceptable interval.

       /etc/courier/filters/ratefilter-maxrcpts
           This file contains a single numerical value that sets how many receipients the same
           sender can send mail to, within the controlling time interval. The default value is
           100 recipients.

       /etc/courier/filters/ratefilter-minuid
           When ratefilter is enabled for locally originating mail, this sets the minimum system
           userid that has rate limiting enforced. The default value is 100. Mail sent by
           processes with lower uids are not subject to rate limiting.

       /etc/courier/filters/ratefilter-mode
           If this file exists and contains the word "all", ratefilter creates its listening
           socket in /var/lib/courier/allfilters, otherwise the socket gets created in
           /var/lib/courier/filters, see courierfilter(8)[1] for more information.

       The enablefiltering settings controls whether local or ESMTP mail is subject to rate
       limiting, see courier(8)[2] for more information.

       In this context, “local” mail refers to mail that gets sent when a process executes the
       sendmail(1)[3] command. This does not include mail sent via connection to local port 25,
       this is considered ESMTP mail.

       Local mail gets rate limited based on the sending process's userid. Each numerical userid
       gets treated as an individual sender.  ESMTP mail's sender is taken from the authenticated
       ESMTP's userid. Non-authenticated ESMTP mail is not subject to rate limiting.

       Rate limiting is implemented by dividing chronological time into intervals that are half
       the time interval given in the ratefilter-interval setting. For example, with the default
       interval of sixty seconds, chronological time gets divided into thirty second intervals.

       ratefilter counts the number of receipients in each message (and not just the number of
       messages) from each sender, in each time interval.

       ratefilter rejects the message when the total number of recipients from all messages from
       the same sender in the current and the previous time interval exceeds the
       ratefilter-maxrcpts setting. The rejected message's number of recipients also get counted,
       for the purpose of rejecting future messages.

SEE ALSO

       courierfilter(8)[1].

AUTHOR

       Sam Varshavchik
           Author

NOTES

        1. courierfilter(8)
           http://www.courier-mta.org/courierfilter.html

        2. courier(8)
           http://www.courier-mta.org/courier.html

        3. sendmail(1)
           http://www.courier-mta.org/sendmail.html