Lib.rs

› Database interfaces | Email
#rate-limiting #user #server #postfix #milter

app postfix_ratelimit

A Postfix milter for rate limiting

Owned by simon0302010.

3 releases

Uses new Rust 2024

0.1.2 Jan 1, 2026
0.1.1 Dec 29, 2025
0.1.0 Dec 28, 2025

#2 in #user

GPL-3.0-only

39KB
830 lines

Postfix_Ratelimit

A Milter for Postfix that limits the number of emails sent from a user within a specified time frame.

Features

  • Limits the number of emails sent per user
  • Configurable time frame and email limit
  • Supports serving multiple Postfix/Sendmail servers

Installation

  1. Install the binary

    cargo install postfix_ratelimit
cp ~/.cargo/bin/postfix_ratelimit /usr/local/bin/postfix_ratelimit

  2. Create a configuration file at /etc/postfix_ratelimit.conf or /usr/local/etc/postfix_ratelimit.conf with the following content:

    # Please change the paths and values as needed
db_file = "/path/to/your/postfix_ratelimit.db"
log_file = "/path/to/your/postfix_ratelimit.log" # Optional but recommended
interval = 60          # Time window in minutes
limit = 20             # Max emails allowed in the time window

Please see the Configuration section for all available options.

  1. See the Postfix documentation for setting up the Milter in Postfix.

Usage

You can now run the Milter with the following command:

postfix_ratelimit

You can also create a service to run it in the background.

Signals

You can send different signals to the program to control it:

  • SIGUSR1 (10) prints the currently loaded configuation values to the console
  • SIGUSR2 (12) resets all rate limits by clearing the database
  • SIGHUP (1) restarts the program to reload the configuration file or save the database
  • Termination Signals (2, 3, 15) save the database and stop the program

Configuration

You can configure options like this:

option = value

Options

Option Type Default Description
db_file String (none, required) Path to the SQLite database file used for storing rate limit data. This option must be set manually.
socket String "inet:127.0.0.1:11847" Address on which the milter will listen, specified as either "inet:IP:PORT" for a TCP socket or "unix:/path/to/socket" for a Unix socket.
interval u64 60 Time window for rate limiting, specified in minutes.
limit u64 20 Maximum number of emails allowed to be sent within each interval.
max_recipients u64 20 Maximum number of recipients allowed per individual email message. 0 for no limit.
count_recipients bool true If true, each recipient counts separately towards the rate limit, causing the limit to be reached faster with emails sent to multiple recipients.
per_host bool false If true, rate limiting is tracked separately per sender and per connecting host; if false, only the sender's email address is considered.
use_sasl bool false Enables rate limiting based on the SASL user. This requires the server to provide the {auth_authen} macro.
clean_interval u64 120 Frequency, in minutes, at which expired entries are removed from the database. Does not affect ratelimiting.
log_file String (none, optional) File path to write logs. Leave empty for no logging to file.
debug bool false Enables Debug mode which prints extra messages to the terminal.
reject_error bool false Rejects emails that encountered some kind of issue during processing like the sender missing. False by default.

CLI Options

--config="

Dependencies

~11–18MB
~242K SLoC