About Rmilter

Introduction

Rmilter is used to integrate rspamd and milter compatible MTA, for example Postfix or Sendmail. It also performs other useful functions for email filtering including:

Virus scanning using Clamav
Spam scanning using Rspamd
Greylisting using redis storage
Ratelimit using redis storage
Replies check (whitelisting replies to sent messages)
Passing certain messages to redis pub/sub channels
DKIM signing

Rmilter project page can be found on GitHub: http://github.com/vstakhov/rmilter.

Rmilter configuration

Rmilter configuration format is described in the following page.

Postfix settings

Here is a scheme that demonstrates Rspamd and Rmilter integration using Postfix MTA:

There are several useful settings for postfix to work with this milter:

smtpd_milters = unix:/var/run/rmilter/rmilter.sock
milter_mail_macros =  i {mail_addr} {client_addr} {client_name} {auth_authen}
milter_protocol = 6

Useful rmilter recipies

This section contains a number of useful configuration recipes and best practices for Rmilter.

Setup DKIM signing of outcoming email for authenticated users

With this setup you should generate keys and store them in /etc/dkim/<domain>.<selector>.key This could be done, for example by using opendkim-genkey:

opendkim-genkey --domain=example.com --selector=dkim

That will generate dkim.private file with private key and dkim.txt with the suggested TXT record for your domain.

dkim {
    domain {
      key = /etc/dkim;
      domain = "*";
      selector = "dkim";
    };
    header_canon = relaxed;
    body_canon = relaxed;
    sign_alg = sha256;
};

Please note, that Rmilter will sign merely mail for the authenticated users, hence you should also ensure that {auth_authen} macro is passed to milter on MAIL FROM stage:

milter_mail_macros =  i {mail_addr} {client_addr} {client_name} {auth_authen}

Setup whitelisting of reply messages

It is possible to store Message-ID headers for authenticated users and whitelist replies to that messages by using of Rmilter. To enable this feature, please ensure that you have redis server running and add the following lines to Redis section:

redis {
  ...
  # servers_id - redis servers used for message id storing, can not be mirrored
  servers_id = localhost;
  # id_prefix - prefix for extracting message ids from redis
  # Default: empty (no prefix is prepended to key)
  id_prefix = "message_id.";
}

citrin / rmilter