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+# Rspamd modules
+
+Rspamd ships with a set of modules. Some modules are written in C to speedup
+complex procedures while others are written in lua to reduce code size.
+Actually, new modules are encouraged to be written in lua and add the essential
+support to the Lua API itself. Truly speaking, lua modules are very close to 
+C modules in terms of performance. However, lua modules can be written and loaded
+dynamically.
+
+## C Modules
+
+C modules provides core functionality of rspamd and are actually statically linked
+to the main rspamd code. C modules are defined in the `options` section of rspamd
+configuration. If no `filters` attribute is defined then all modules are disabled.
+The default configuration enables all modules explicitly:
+
+~~~nginx
+filters = "chartable,dkim,spf,surbl,regexp,fuzzy_check";
+~~~
+
+Here is the list of C modules available:
+
+- [regexp](regexp.md): the core module that allow to define regexp rules,
+rspamd internal functions and lua rules.
+- [surbl](surbl.md): this module extracts URLs from messages and check them against
+public DNS black lists to filter messages with malicious URLs.
+- [spf](spf.md): checks SPF records for messages processed.
+- [dkim](dkim.md): performs DKIM signatures checks.
+- [fuzzy_check](fuzzy_check.md): checks messages fuzzy hashes against public blacklists.
+- [chartable](chartable.md): checks character sets of text parts in messages.
+
+## Lua modules
+
+Lua modules are dynamically loaded on rspamd startup and are reloaded on rspamd
+reconfiguration. Should you want to write a lua module consult with the 
+[Lua API documentation](../lua/). To define path to lua modules there is a special section
+named `modules` in rspamd:
+
+~~~nginx
+modules {
+  path = "/path/to/dir/";
+  path = "/path/to/module.lua";
+  path = "$PLUGINSDIR/lua";
+}
+~~~
+
+If a path is a directory then rspamd scans it for `*.lua" pattern and load all
+files matched.
+
+Here is the list of Lua modules shipped with rspamd:
+
+- [multimap](multimap.md) - a complex module that operates with different types
+of maps.
+- [rbl](rbl.md) - a plugin that checks messages against DNS blacklist based on
+either SMTP FROM addresses or on information from `Received` headers.
+- [emails](emails.md) - extract emails from a message and checks it against DNS
+blacklists.
+- [maillist](maillist.md) - determines the common mailing list signatures in a message.
+- [once_received](once_received.md) - detects messages with a single `Received` headers
+and performs some additional checks for such messages.
+- [phishing](phishing.md) - detects messages with phished URLs.
+- [ratelimit](ratelimit.md) - implements leaked bucket algorithm for ratelimiting and
+uses `redis` to store data.
+- [trie](trie.md) - uses suffix trie for extra-fast patterns lookup in messages.
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