最终效果

如下，能够使我们发送的邮件直接到达对方的收件箱，而不是被当作垃圾邮件。

制作DKIM密钥

使用openssl生成我们所需要的Private Key和Public Key。

X:\sign>openssl genrsa -out rsa.private 1024
WARNING: can’t open config file: /home/drangon/work/mingw-w64-dgn/lib_bin/openssl/ssl/openssl.cnf
Loading ‘screen’ into random state – done
Generating RSA private key, 1024 bit long modulus
………………++++++
…………………………..++++++
e is 65537 (0x10001)
X:\sign>openssl rsa -in rsa.private -out rsa.public -pubout -outform PEM
WARNING: can’t open config file: /home/drangon/work/mingw-w64-dgn/lib_bin/openssl/ssl/openssl.cnf
writing RSA key

这样得到rsa.private和rsa.public两个文本文件。

域名配置DKIM

在域名控制面板，除了需要给域名（例如xsign.org）设置MX记录，还要添加一项dkim的TXT记录。
假设dkim的Selector是s1（可以有多个Selector，表示可以使用多个dkim证书），则要设置的是：

s1._domainkey.xsign.org TXT

内容为：

k=rsa; t=y; p=[Public Key的内容]

可以使用nslookup检查是否已经生效。

I:\Users\Administrator>nslookup
默认服务器: ns3.gd.cnmobile.net
Address: 221.179.38.7

> set type=TXT
> s1._domainkey.xsign.org
服务器: ns3.gd.cnmobile.net
Address: 221.179.38.7

非权威应答:
s1._domainkey.xsign.org text =

"t=y; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC1OmB7qZbFWqAgl51jS
U0Opn/wdJaB2mTkkPgD+gW3ccjXTazgYZVkokCeD+67oceWw42mLTkzg402Vc+IaIk+L57GULVxzECw8
mWtR7jOcG3UOnuaRMScX8uRlnllXj6v1SQTHljW2M++D/hj3dn8lDWxWw0s8IbesSb3far8XQIDAQAB"

SMTP发送代码

需要用到python的dkim库和dnspython.org提供的dns库。

import smtplib, email, dkim
import dns.resolver

def sendmail(mailfrom, mailto, msg):
    domain = email.Utils.unquote(mailto).split("@")[1]
    host = dns.resolver.query(domain, "MX")[0].exchange
    smtp = smtplib.SMTP(str(host))
    smtp.sendmail(mailfrom, [mailto], msg)
    smtp.quit()

if __name__ == "__main__":
    msg = "From: xiaoxia@xsign.org\r\n" \
        "To: gdxxhg@gmail.com\r\n" \
        "Subject: Hi\r\n\r\n" \
        "I miss you!!!!\r\n"
    sig = dkim.sign(msg, "s1", "xsign.org", open("./rsa_private.txt").read())
    msg = sig + msg
    print msg
    sendmail("xiaoxia@xsign.org", "gdxxhg@gmail.com", msg)
    print "ok"

运行程序，即发送了一封邮件到gdxxhg@gmail.com的收件箱里。

验证DKIM

GMail里可以看到dkim的验证已经通过！

Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning xiaoxia@xsign.org does not designate 120.196.50.109 as permitted sender) smtp.mail=xiaoxia@xsign.org; dkim=pass (test mode) header.i=@xsign.org
Date: Tue, 24 May 2011 10:51:43 -0700 (PDT)
Message-Id: <4ddbf02f.c45bdc0a.6271.6877SMTPIN_ADDED@mx.google.com>
DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=xsign.org;
i=@xsign.org; q=dns/txt; s=s1; t=1306259500; h=From : To : Subject;
bh=5yC7rMxS78DH//OfCDEEHnf4nFVZ21IFPtApH3ARSkg=; b=ASqTJBKbhDzVcj59AYR7kUI7WF+o5GJHje5iN6JqiCtVTk/DQaft58sridQu4YMTFfadmuPRnUfGia/CU2nJFnzeJmGq9nQIRctwsLdUWIKGxc5xp3eZ0H4rU57WAuDJPRQdea7Vaf4sNotDHEldKC1lHsSgdROYbhE12CZjNpI=
From: xiaoxia@xsign.org
To: gdxxhg@gmail.com
Subject: Hi

I miss you!!!!