OpenDKIM是一个开源的DKIM发送者认证系统的C语言实现。
DKIM（DomainKeys ">Identified Mail）是一种电子邮件的验证技术，使用密码学的基础提供了签名与验证一般来说，发送方会在电子邮件的标头插入DKIM-Signature及电子签名资讯。
OpenDKIM 2.4.0发行说明：
Feature request #SF3060140: Extension of odkim.sign() to include maximum signed byte count.
Feature request #SF3171865: Add _FFR_LUA_GLOBALS, enabling a mechanism to maintain state between Lua scripts.
Feature request #SF3241982: Optionally add an Authentication-Results field for all signatures present, not just the first good one.
Feature request #SF3256630: Add _FFR_RATE_LIMIT, enabling hooks for post-verification rate controls.
Feature request #SF3290461: Add optional support for querying a memcache daemon via libmemcached.
Feature request #SF3299041: Be tougher on use of the "l=" tag by removing "BodyLengths", renaming "BodyLengthDBFile" to "BodyLengthDB", and allowing pattern matches. This effectively activates _FFR_BODYLENGTH_DB as well.
Feature request #SF3303911: Add "DisableADSP" setting.
In the stats recording code, only check for a domain match for signatures that don't have errors (i.e., short circuit if sigerror is not zero).
LIBOPENDKIM: Feature request #SF2969516: Teach dkim_chunk() about DKIM_LIBFLAGS_FIXCRLF.
LIBOPENDKIM: Feature request #SF3123731: Extend FixCRLF to cover header fields.
LIBOPENDKIM: Feature request #SF3151534: Extract DKIM reputation support to its own library.
LIBOPENDKIM: Feature request #SF3279589: Add _FFR_XTAGS, adding support for generic extension tags in signatures.
LIBOPENDKIM: Feature request #SF3300738: Add dkim_sig_getqueries() and dkim_policy_getqueries() to assist API consumers that have their own DNS mechanisms not directly adaptable to ours. Requested by Heikki Gruner.
LIBOPENDKIM: Return an error from dkim_getsighdr() or dkim_getsighdr_d() if called after a key load failure. Problem noted by Heikki Gruner.
LIBAR: Check that the descriptor's write socket is writable before calling ar_sendquery() when trying to identify open requests that need retransmission.
STATS: Feature request #SF3066106: Add "opendkim-anonstats" tool.
CONTRIB: Paths in init/redhat/opendkim are now auto-generated.
Activate _FFR_MAXVERIFY.
下载地址：
http://sourceforge.net/projects/opendkim/files/opendkim-2.4.0.tar.gz/download
http://sourceforge.net/projects/opendkim/files/opendkim-2.4.0.tar.gz.md5/download
http://sourceforge.net/projects/opendkim/files/opendkim-2.4.0.tar.gz.asc/download