An alternative introduction to rspamd configuration - this guide delves into the intricacies of Rspamd configuration files and their significance from a sysadmin perspective, focusing on the crucial inquiries of “What can be configured?” and “How do I go about configuring it?”.
Own mail server based on Dovecot, Postfix, MySQL, Rspamd and Debian 9 Stretch - this manual serves as a comprehensive tutorial for setting up your own mail server. It is important to note that the suggestion of adding level = error to /etc/rspamd/local.d/logging.inc is not correct. In most cases, it is advisable to utilize the default info level or opt for silent if you only wish to log crucial information.
First of all, you need a working MTA that can send and receive email for your domain using SMTP protocol. This guide covers the setup of the Postfix MTA, but note that Rspamd can also work with other MTA software. For more information, see the integration document. Keep in mind that Exim MTA has limited support for Rspamd, so it’s not recommended to run them together.
It is highly recommended to set up Transport Layer Security (TLS) for your mail system. To make it easy to manage, we suggest using certificates issued by Let’s Encrypt. For more information on this topic, you can refer to online guides such as this one.
Please note that this guide assumes that all services have the same certificate, which might not be optimal for higher security needs.
Postfix setup
It is assumed that you are using your operating system’s package manager (e.g. apt install postfix) to install Postfix. The following configuration is desired for Postfix:
For IMAP we recommend to install Dovecot. If you’re using a Debian-based system, you can use the following packages:
apt install dovecot-imapd dovecot-sieve
Configuring Dovecot, particularly its authentication mechanisms, is beyond the scope of this guide. However, you can find many helpful guides on the Dovecot main site. By default, Dovecot uses Unix users in system and place mail into the standard mailbox /var/mail/username.
It is important to set up Postfix authentication as well. This is located in /etc/dovecot/conf.d/10-master.conf. Ensure that the following lines in this file are uncommented:
Additionally, it is recommended to set up Transport Layer Security (TLS) to protect passwords and other sensitive information from being transmitted over insecure connections.
whitelisting of reply messages (storing reply message IDs to avoid certain checks for replies to our own sent messages)
Installation of Redis is quite straightforward: install it using the preferred way for your OS (e.g. from packages), start redis-server with the default settings (it should listen on the local interface using port 6379) and you are done.
We highly recommend using separate Redis instance for each module that stores non-volatile data, specifically for the statistical module (BAYES classifier) and fuzzy storage. This multi-instance Redis configuration simplifies administration tasks such as backup and restore, and allows for setting memory limits and eviction policies, as well as establishing data replication between Rspamd installations. For more information on configuring multiple Redis instances, refer to the Redis replication tutorial.
It may also be a good idea to limit the memory used by Redis to a reasonable value, such as:
maxmemory 500mb
Additionally, for Redis instances storing non-volatile data, you might consider setting the volatile-ttl eviction policy:
maxmemory-policy volatile-ttl
Keep in mind that eviction of volatile data keys can cause undesirable effects.
It’s important to note that Redis may listen for connections from all network interfaces by default, which can be a security risk. To limit this to the loopback interfaces, use the following configuration directive:
bind 127.0.0.1 ::1
To ensure data is saved to disk, it may also be beneficial to set up overcommit memory behavior, especially for systems under heavy load. This can be done in Linux using the following command:
echo 1 > /proc/sys/vm/overcommit_memory
Rspamd installation
Instructions for downloading Rspamd can be found on the downloads page. This page includes information on how to obtain Rspamd, how to install it on your system, and an alternative method of building Rspamd from source.
Packaging should include starting Rspamd and configuring it to run automatically on startup during installation.
To confirm that Rspamd is running, you can use the following command:
systemctl status rspamd
Configuring Rspamd
While Rspamd’s default configuration is designed to be suitable for most use cases, you may want to make some adjustments to better suit your specific needs or preferences.
Using of configwizard
Starting from version 1.7, a configuration wizard is available as an rspamadm subcommand. This wizard can assist you in configuring popular features in Rspamd, such as:
Redis server
Controller password
DKIM signing for outbound
To run the wizard, use the following command:
rspamadm configwizard
This tool will guide you interactively throughout the configuration process using CLI interface.
Manual configuration
Firstly, refer to the principles of basic configuration here for further reading.
Additionally, it is advisable to utilize the specialized include files as referenced in the default configuration. Typically, each configuration file located in the directory /etc/rspamd/ will incorporate two such includes:
# /etc/rspamd/modules.d/imaginary_module.confimaginary_module{# there would probably be some settings in this area.include(try=true,priority=1,duplicate=merge)"$CONFDIR/local.d/imaginary_module.conf".include(try=true,priority=10)"$CONFDIR/override.d/imaginary_module.conf"}
Settings in local.d will be merged with stock configuration (where possible: ie. the setting is a list [] or collection {}) where-as settings in override.d will always replace the stock configuration. Unlike rspamd.conf.local and rspamd.conf.override, these include directives are effective inside a given block of configuration ({}). Similarly to rspamd.conf.override settings in override.d have higher priority than settings generated by the web interface, unlike local.d and rspamd.conf.local.
Overriding symbols scores and actions thresholds
You can gain further insight on actions, scores, and related configuration parameters by reading this explanation.
Starting from Rspamd version 1.7, the thresholds setup can be edited in the file local.d/actions.conf:
# local.d/actions.confreject=150;# Reject when reaching this scoreadd_header=6;# Add header when reaching this scoregreylist=4;# Apply greylisting when reaching this score (will emit `soft reject action`)
For symbols scores, you should redefine scores defined in scores.d/ directory where they are placed by a symbol’s group:
fuzzy_group.conf - fuzzy hashes scores
headers_group.conf - various headers checks
hfilter_group.conf - host filter symbols
mime_types_group.conf - mime types rules
mua_group.conf - MUA related rules
neural_group.conf - neural network produced scores
The weights of rules can also be modified through the Rspamd WebUI. To obtain current information about symbols and scores, the command rspamc counters can be utilized.
For those who wish to create their own rule or simply adjust the score without considering groups, the file local.d/groups.conf can be used in the following manner:
# /etc/rspamd/local.d/groups.conf# Just scores for Rspamd defined symbolssymbols={"R_DKIM_ALLOW"={score=-0.1;}"BAYES_SPAM"={score=5.0;}}# Custom user defined symbols and groupsgroup"mygroup"{symbols={"FOO"{score=20.0;}}}
One more note about scores
There are two components of the final score in Rspamd:
score = runtime_score * static_score
Runtime score is a term used to indicate the level of confidence. For example, if you have an IP reputation that varies within the range of [-1;1], and you set the static score for IP reputation to 3.0, then the resulting score would be:
This eliminates the need to define specific scores such as
IP_SCORE_TOO_BAD
IP_SCORE_BAD
IP_SCORE_SOMEHOW_BAD
… etc. to differentiate the level of reputation.
Other configuration advice
You should notice that individual files are included within sections:
module { .include "..."; }
Hence, you don’t need to repeat module { ... } inside the included file! Rspamd will issue an error in this case: nested section: module { module { ... } }, it is likely a configuration error.
In addition to equivalents to files in /etc/rspamd/modules.d the following includes are referenced in the stock configuration (both of local.d/override.d):
classifier-bayes.conf: included inside classifier "bayes" {} block
logging.inc: included inside logging { }
options.inc: included inside options { }
worker-normal.inc: included inside normal worker {} block
worker-controller.inc: included inside controller worker {} block
worker-proxy.inc: included inside rspamd_proxy worker {} block
Setting listening interface
Rspamd’s normal worker will, by default, listen on all interfaces on port 11333. From Rspamd 1.7.4, it has changed to localhost by default.
If Rspamd is running on the same machine as the mailer or any other application that will be querying it, it is recommended to set this option to ‘localhost’. This option should be defined in /etc/rspamd/local.d/worker-normal.inc:
If you choose to keep the default settings, it is recommended to use a firewall to restrict access to the machine. For further information on bind_socket and related settings, please refer to the worker documentation.
By default, the Rspamd controller worker listens on port 11334, and the proxy worker uses port 11332.
As Rspamd does not perform certain checks for local networks, it may be necessary to adjust the global local_addrs map accordingly.
# /etc/rspamd/local.d/options.inc# Local networks (default)local_addrs="192.168.0.0/16, 10.0.0.0/8, 172.16.0.0/12, fd00::/8, 169.254.0.0/16, fe80::/10";
Rspamd requires a password when queried from non-trusted IP addresses, with the exception of scanning messages which are unrestricted (the default configuration trusts the loopback interface). This is configured in the file /etc/rspamd/local.d/worker-controller.inc.
For better security, it is recommended to store an encrypted password. To generate such a password, you can use the following command:
$ rspamadm pw
Enter passphrase:
$2$g95ywihfinjqx4r69u6mgfs9cqbfq1ay$1h4bm5uod9njfu3hdbwd3w5xf5d9u8gb7i9xnimm5u8ddq3c5byy
The configuration to be modified is shown below, you should replace the password with the output generated from your chosen password:
By setting the enable_password option, data-changing operations, such as Bayes training or fuzzy storage, will require a password for execution. For example:
From version 1.7, the setting of passwords is also suggested by rspamadm configwizard.
Important information: the default passwords (namely, q1 and q2) are BANNED, so you cannot use them in your installation. Please set the appropriate passwords before using the controller. This is done to prevent an occasional data leak caused by misconfiguration.
Setting up the WebUI
The WebUI is managed by a controller worker, but for added functionality such as TLS support, it may be beneficial to proxy its requests through a tool like Nginx. Below is a minimal configuration needed to accomplish this using Nginx:
Alternatively, you could set up HTTP authentication in Nginx itself.
Using of Milter protocol (for Rspamd >= 1.6)
“Starting with Rspamd 1.6, the rspamd proxy worker supports the milter protocol, which is supported by popular MTAs such as Postfix and Sendmail. This feature also renders the rmilter project obsolete in favor of the new integration method. The milter protocol is available only in rspamd_proxy, however, there are two ways to use this protocol:
Proxy mode (for large instances) with a dedicated scan layer
Self-scan mode (for small instances)
Here, we describe the simplest self-scan option:
In this mode, rspamd_proxy scans messages itself and talks to MTA directly using the Milter protocol. The advantage of this approach is its simplicity. Here is a sample configuration for this mode:
# local.d/worker-proxy.incmilter=yes;# Enable milter modetimeout=120s;# Needed for Milter usuallyupstream"local"{default=yes;# Self-scan upstreams are always defaultself_scan=yes;# Enable self-scan}count=4;# Spawn more processes in self-scan modemax_retries=5;# How many times master is queried in case of failurediscard_on_reject=false;# Discard message instead of rejectionquarantine_on_reject=false;# Tell MTA to quarantine rejected messagesspam_header="X-Spam";# Use the specific spam headerreject_message="Spam message rejected";# Use custom rejection message
For more advanced proxy usage, please see the corresponding documentation.
Setup Redis statistics
Starting with version 1.1, it is now possible to utilize Redis as a backend for statistics and caching of learned messages. Redis is particularly recommended for clustered configurations as it enables concurrent learning and checking, and also performs very quickly. To configure Redis, you can specify the redis backend for a classifier, and the cache will automatically be set to the same servers.
Rspamd also boasts dynamic map support, which allows for lists of values such as domain names or IP/networks to be stored in external files or accessed via HTTP and periodically monitored by Rspamd for updates. This feature is useful for creating custom rules, whitelisting or blacklisting specific networks, among other use cases. An important aspect of maps is that they do not require a Rspamd restart to take effect when the lists are modified. Maps are defined as URI strings:
http://example.com/file.map - HTTP map (server should respect If-Modified-Since header to avoid unnecessary updates)
file:///path/to/map - file map
/path/to/map - alternative syntax for file map
All maps behaves in the same way so you can have some choices about how to define a map:
Plain path to file or http (like map = "http://example.com/file.txt" or map = "/tmp/mymap")
Composite path like map = ["http://example.com/file.txt", "/tmp/mymap"]. Maps data is concatenated from the sources.
An embedded map like map = ["foo bar"]; or map = ["foo 1", "bar b", "baz bababa"] or map = ["192.168.1.1/24", "10.0.0.0/8"]
A fully decomposed object with lots of options
For the second option it is also possible to have a composite path with a fallback:
In the example above fallback+file://${CONFDIR}/2tld.inc will be used when the first composite backend is somehow unreachable (e.g. when the first load of Rspamd or all elements are invalid).
Bear in mind that (1) and (3) can only be distinguished by making an array-like map = ["192.168.1.1/24"]
Historically just for the radix map (IP network ones) you could also use map = "192.168.1.1/24" but it is not recommended.
Within maps, you can use whitespace or comments. For example, here is an example of IP/network map:
# Example map
127.0.0.1 # localhost
10.0.0.0/8
fe80::/64
There is a special module called multimap that allows you to define your maps without writing Lua rules. You can check the module’s documentation and create your configuration in local.d/multimap.conf.
Configuring RBLs
While Rspamd is free to use for any purpose, it is important to note that some of the RBLs included in the default configuration may require a fee or have usage restrictions. It is crucial to ensure that your use of these RBLs does not violate any rights. The following notes provide additional information about limitations of specific RBLs enabled in the default configuration (you can follow the links for more details):
DNSWL - Commercial use forbidden (see link for definition); Limit of 100k queries per day
Mailspike - Limit of 100k messages or queries per day
MSBL EBL - Organizations that have over 100 users should contact the reseller to arrange for commercial access
Rspamd URIBL - Commercial use forbidden (see link for definition); Limit of 250k queries per day
SORBS - Limit of 100k users or more than 5 messages per second sustained
SpamEatingMonkey - Limit of 100k queries per day or more than 5 queries per second for more than a few minutes
Spamhaus - Commercial use forbidden (see link for definition); Limit of 300k queries or 100k SMTP connections per day
SURBL - Commercial use forbidden (see link for definition); Limit of 1k users or 250k queries per day
UCEProtect - If you’re sending 100k queries or more per day you should use the (free) Rsync service.
URIBL - Requires a commercial subscription if ‘excessive queries’ are sent (numbers unclear).
Refer to the RBL module documentation for information about disabling RBLs/SURBLs.
The following RBLs are not enabled in the default configuration but may be enabled via additional configuration:
Abusix Mail Intelligence - Free for home/non-commercial use up to 100k queries per day (requires registration), commercial use requires a subscription
Using Rspamd
Using rspamc console routine
rspamc implements a feature-complete client for Rspamd. For detailed documentation refer to man rspamc.
Rspamadm is a utility that enables direct management of Rspamd. It includes an embedded help feature, which can be accessed by typing:
% rspamadm help
Rspamadm 2.6
Usage: rspamadm [global_options] command [command_options]
Available commands:
configdump Perform configuration file dump
configgraph Produces graph of Rspamd includes
confighelp Shows help for configuration options
configtest Perform configuration file test
configwizard Perform guided configuration for Rspamd daemon
control Manage rspamd main control interface
cookie Produces cookies or message ids
corpustest Create logs files from email corpus
dkim_keygen Create dkim key pairs
dnstool DNS tools provided by Rspamd
fuzzyconvert Convert fuzzy hashes from sqlite3 to redis
grep Search for patterns in rspamd logs
keypair Manages keypairs for Rspamd
lua Run LUA interpreter
mime Mime manipulations provided by Rspamd
pw Manage rspamd passwords
signtool Sign and verify files tool
statconvert Convert statistics from sqlite3 to redis
template Apply jinja templates for strings/files
vault Perform Hashicorp Vault management
For example, it is possible to get help for a specific configuration option by typing something like
rspamadm confighelp -k fuzzy
See here for more information about rspamadm utilities.
Using mail system utilities
It is also useful to have a simple Sieve script to place all messages marked as spam in the Junk folder. Here is an example of such a script (~/.dovecot.sieve):
It is also possible to set up Rspamc to learn by forwarding messages to a specific email address. I recommend using /etc/aliases for these purposes and mail-redirect command (e.g. provided by Mail Redirect addon for Thunderbird MUA). The desired aliases could be the following:
It is important to use less predictable aliases to prevent messages from being sent to these addresses by an adversary or accidentally, in order to avoid contamination of the statistics.
There is also an add-on for Thunderbird MUA written by Alexander Moisseev to visualise Rspamd stats. You can download the latest version from its homepage or a version reviewed by moz://a from Tunderbird Add-ons page. You’d need to add extended spam headers (X-Spamd-Result) with Rspamd proxy worker and/or (from add-on’s version 0.8.0) X-Spam-Score and X-Spam-Report headers with Exim to make the whole setup work.
To enable extended spam headers in Milter headers module add the following line to local.d/milter_headers.conf:
extended_spam_headers=true;
To enable headers in Exim refer to the “Integration with Exim MTA” section of the MTA integration document.
Here is a screenshot of this addon in use:
Using the WebUI
Rspamd has a built-in WebUI which supports setting metric actions and scores; Bayes training and scanning messages - for more information see the WebUI documentation.
Using Rspamd in large email systems
Rspamd, designed for large-scale email systems, offers various features to facilitate the processing of emails for thousands or millions of users. Despite this, its default settings are conservative, making it suitable for smaller systems as well.
We recommend obtaining official Rspamd packages from the https://www.rspamd.com website if you are using a Debian-based Linux distribution. These packages are optimized for performance and feature sets. For users on other platforms, we advise contacting Rspamd support (mailto://support@rspamd.com) with your specific needs. There may be optimized packages available for your platform that have not yet been built.
In addition to obtaining optimized Rspamd packages, it is also recommended to set up Redis. Typically, two types of Redis instances are needed:
Master-slave replicated instances for persistent data: statistics, fuzzy hashes, neural networks. These instances are mostly read-only, so you can distribute the load among read-only slaves.
Non-replicated but (possibly) sharded instances for volatile data: greylisting, replies, IP reputation, and other temporary data. These instances do not need to be persistent and can be scaled through sharding, which Rspamd will automatically perform if you specify multiple servers. These instances have a mixed read-write workload.
For advanced clustering options beyond what Redis Sentinel offers, we recommend considering the KeyDB project. KeyDB is a drop-in replacement for Redis that supports multi-master replication mode, while maintaining full compatibility with Redis (and Rspamd).
You might also want to enable the following modules:
IP score: IP reputation module, requires volatile Redis instance (or shared volatile Redis instance). In some cases, it can provide your results common to the expensive IP DNS blacklists. However, it also depends on the quality of your rules and your scale.
Neural networks: this module provides significant improvement for your filtering quality but it requires CPU resources (SandyBridge or newer Intel CPUs are strongly adviced) and somehow good rules set. It also requires some setup and a persistent Redis instance. From version 2.0 Rspamd uses libkann for neural networks which demonstrates better performance and preciseness than the pre 1.7 implementations based on libfann. Here is a minimal setup for neural networks module:
# local.d/neural.confservers="redis:6384";timeout=25s;# Sometimes ANNs are very largetrain{max_trains=1k;# Number ham/spam samples needed to start trainmax_usages=20;# Number of learn iterations while ANN data is validspam_score=8;# Score to learn spamham_score=-2;# Score to learn hamlearning_rate=0.01;# Rate of learningmax_iterations=100;# Maximum iterations of learning (better preciseness but also lower speed of learning)}ann_expire=2d;# For how long ANN should be preserved in Redis
Ratelimit: this module is highly effective in limiting spam waves, as it allows for temporarily delaying senders with poor reputation or those sending messages too aggressively without a good reputation. A volatile Redis instance is required for its use.
Replies: whitelists replies to your user’s mail. It is very useful to provide users instant communication with known recipients. Requires a volatile Redis instance.
URL redirector: resolves URL redirects on some common redirectors and URLs shorteners, e.g. t.co or goo.gl. Requires a volatile Redis instance.
Clickhouse: saves analytical data to the Clickhouse server. Clickhouse server can be used thereafter to create new filtering rules or maintaining blacklists. It serves as an advanced Syslog with indexes and complex analytics queries. Additionally, there are graphical interfaces available for Clickhouse, such as Redash
