追风之云

先确保sendmail能正常验证
配置如下：
define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')
TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')
define(`confAUTH_OPTIONS', `A')dnl

填写SMART_HOST,
define(`SMART_HOST',`smtp.gmail.com')dnl

设置验证用户
FEATURE(`authinfo',`hash /etc/mail/authinfo.db')

验证用户的格式
AuthInfo:smtp.gmail.com "U:root" "I:votreadresse@gmail.com" "P:mot_de_passe" "M:PLAIN"
AuthInfo:smtp.gmail.com:587 "U:root" "I:votreadresse@gmail.com" "P:mot_de_passe" "M:PLAIN"

生成验证用户文件的db格式
makemap hash /etc/mail/authinfo < /etc/mail/authinfo
chmod 600 /etc/mail/authinfo

设置好后重启sendmail

使用中会产生类似如下的log
发送服务器
to=<发送邮箱>, delay=00:00:07, xdelay=00:00:07, mailer=relay, pri=120309, relay=转发服务器域名. [转发服务器IP], dsn=2.0.0, stat=Sent (p9TDlO0P003601 Message accepted for delivery)


转发服务器
to=<发送邮箱>, delay=00:00:04, xdelay=00:00:03, mailer=esmtp, pri=120465, relay=mx3.qq.com. [112.90.141.240], dsn=2.0.0, stat=Sent (Ok: queued as )


参考资料：
http://www.tux89.com/telephonie/configurer-sendmail-comme-relais-smtp-vers-la-messagerie-gmail/?lang=en
http://blog.chinaunix.net/space.php?uid=8721861&do=blog&id=2017181
http://www.cyberciti.biz/faq/configure-sendmail-as-a-smart-host/
http://dbabc.net/archives/2010/10/20/rhel4-sendmail-replay.shtml
http://hi.baidu.com/17ppc/blog/item/b34496987afb801f6f068c10.html