实测灰名单到底做了什么。

wxhsh

测试环境 ：MD9.52pro/2003sp2/sql2005sp2
启用灰名单，使用默认设置：
总公司发一封信给本域帐号，总公司有反解，有SPF记录
日志如下（关键部分用X处理）：

Fri 2008-03-14 14:39:31: Session 9845; child 2; thread 1944
Fri 2008-03-14 14:39:30: 接受 SMTP 连接来自 [x.x.x.x ：3946]
Fri 2008-03-14 14:39:30: Performing PTR lookup (x.x.x.x.IN-ADDR.ARPA)
Fri 2008-03-14 14:39:30: *  D=x.x.x.x.IN-ADDR.ARPA TTL=(932) PTR=[mail.x.com]
Fri 2008-03-14 14:39:30: *  Gathering A records...
Fri 2008-03-14 14:39:30: *  D=mail.x.com TTL=(112) A=[x.x.x.x]
Fri 2008-03-14 14:39:30: ---- End PTR results
Fri 2008-03-14 14:39:30: --> 220 x.com ESMTP MAIL ready
Fri 2008-03-14 14:39:30: <-- EHLO mail.x.com
Fri 2008-03-14 14:39:30: Performing IP lookup (mail.x.com)
Fri 2008-03-14 14:39:30: *  D=mail.x.com TTL=(112) A=[x.x.x.x]
Fri 2008-03-14 14:39:30: ---- End IP lookup results
Fri 2008-03-14 14:39:30: --> 250-x.com Hello mail.x.com, pleased to meet you
Fri 2008-03-14 14:39:30: --> 250-ETRN
Fri 2008-03-14 14:39:30: --> 250-AUTH=LOGIN
Fri 2008-03-14 14:39:30: --> 250-AUTH LOGIN CRAM-MD5
Fri 2008-03-14 14:39:30: --> 250-8BITMIME
Fri 2008-03-14 14:39:30: --> 250-STARTTLS
Fri 2008-03-14 14:39:30: --> 250 SIZE 0
Fri 2008-03-14 14:39:30: <-- MAIL From:<xx@x.com> SIZE=56661
Fri 2008-03-14 14:39:30: Performing IP lookup (xx.com)
Fri 2008-03-14 14:39:30: *  D=xx.com TTL=(436) A=[x.x.x.x]
Fri 2008-03-14 14:39:31: *  P=010 S=000 D=xx.com TTL=(190) MX=[mail.x.com] {x.x.x.x}
Fri 2008-03-14 14:39:31: ---- End IP lookup results
Fri 2008-03-14 14:39:31: Performing SPF lookup (xx.com / x.x.x.x)
Fri 2008-03-14 14:39:31: *  xx.com x.x.x.x; matched to SPF cache
Fri 2008-03-14 14:39:31: *  Result: pass
Fri 2008-03-14 14:39:31: ---- End SPF results
Fri 2008-03-14 14:39:31: --> 250 <xx@x.com>, Sender ok
Fri 2008-03-14 14:39:31: <-- RCPT To:<xx@x.com>
Fri 2008-03-14 14:39:31: --> 451 Greylisting enabled, try again in 60 minutes
Fri 2008-03-14 14:39:31: <-- QUIT
Fri 2008-03-14 14:39:31: --> 221 See ya in cyberspace
Fri 2008-03-14 14:39:31: SMTP 会话终止（in/out 字节： 119/319）
Fri 2008-03-14 14:39:31: ----------

Fri 2008-03-14 14:39:36: Session 9847; child 2; thread 2296
Fri 2008-03-14 14:39:36: 接受 SMTP 连接来自 [x.x.x.x ：3966]
Fri 2008-03-14 14:39:36: Performing PTR lookup (x.x.x.x.IN-ADDR.ARPA)
Fri 2008-03-14 14:39:36: *  D=x.x.x.x.IN-ADDR.ARPA TTL=(932) PTR=[mail.x.com]
Fri 2008-03-14 14:39:36: *  Gathering A records...
Fri 2008-03-14 14:39:36: *  D=mail.x.com TTL=(112) A=[x.x.x.x]
Fri 2008-03-14 14:39:36: ---- End PTR results
Fri 2008-03-14 14:39:36: --> 220 x.com ESMTP MAIL ready
Fri 2008-03-14 14:39:36: <-- EHLO mail.x.com
Fri 2008-03-14 14:39:36: Performing IP lookup (mail.x.com)
Fri 2008-03-14 14:39:36: *  D=mail.x.com TTL=(112) A=[x.x.x.x]
Fri 2008-03-14 14:39:36: ---- End IP lookup results
Fri 2008-03-14 14:39:36: --> 250-x.com Hello mail.x.com, pleased to meet you
Fri 2008-03-14 14:39:36: --> 250-ETRN
Fri 2008-03-14 14:39:36: --> 250-AUTH=LOGIN
Fri 2008-03-14 14:39:36: --> 250-AUTH LOGIN CRAM-MD5
Fri 2008-03-14 14:39:36: --> 250-8BITMIME
Fri 2008-03-14 14:39:36: --> 250-STARTTLS
Fri 2008-03-14 14:39:36: --> 250 SIZE 0
Fri 2008-03-14 14:39:36: <-- MAIL From:<xx@x.com> SIZE=56661
Fri 2008-03-14 14:39:36: Performing IP lookup (xx.com)
Fri 2008-03-14 14:39:36: *  D=xx.com TTL=(436) A=[x.x.x.x]
Fri 2008-03-14 14:39:36: *  P=010 S=000 D=xx.com TTL=(190) MX=[mail.x.com] {x.x.x.x}
Fri 2008-03-14 14:39:36: ---- End IP lookup results
Fri 2008-03-14 14:39:36: Performing SPF lookup (xx.com / x.x.x.x)
Fri 2008-03-14 14:39:36: *  xx.com x.x.x.x; matched to SPF cache
Fri 2008-03-14 14:39:36: *  Result: pass
Fri 2008-03-14 14:39:36: ---- End SPF results
Fri 2008-03-14 14:39:36: --> 250 <xx@x.com>, Sender ok
Fri 2008-03-14 14:39:36: <-- RCPT To:<xx@x.com>
Fri 2008-03-14 14:39:36: --> 451 Greylisting enabled, try again in 60 minutes
Fri 2008-03-14 14:39:36: <-- QUIT
Fri 2008-03-14 14:39:36: --> 221 See ya in cyberspace
Fri 2008-03-14 14:39:36: SMTP 会话终止（in/out 字节： 119/319）
Fri 2008-03-14 14:39:36: ----------
Fri 2008-03-14 14:39:47: Session 9848; child 2; thread 2512
Fri 2008-03-14 14:39:46: 接受 SMTP 连接来自 [x.x.x.x ：3988]
Fri 2008-03-14 14:39:46: Performing PTR lookup (x.x.x.x.IN-ADDR.ARPA)
Fri 2008-03-14 14:39:46: *  D=x.x.x.x.IN-ADDR.ARPA TTL=(932) PTR=[mail.x.com]
Fri 2008-03-14 14:39:46: *  Gathering A records...
Fri 2008-03-14 14:39:46: *  D=mail.x.com TTL=(112) A=[x.x.x.x]
Fri 2008-03-14 14:39:46: ---- End PTR results
Fri 2008-03-14 14:39:46: --> 220 x.com ESMTP MAIL ready
Fri 2008-03-14 14:39:46: <-- EHLO mail.x.com
Fri 2008-03-14 14:39:46: Performing IP lookup (mail.x.com)
Fri 2008-03-14 14:39:46: *  D=mail.x.com TTL=(112) A=[x.x.x.x]
Fri 2008-03-14 14:39:46: ---- End IP lookup results
Fri 2008-03-14 14:39:46: --> 250-x.com Hello mail.x.com, pleased to meet you
Fri 2008-03-14 14:39:46: --> 250-ETRN
Fri 2008-03-14 14:39:46: --> 250-AUTH=LOGIN
Fri 2008-03-14 14:39:46: --> 250-AUTH LOGIN CRAM-MD5
Fri 2008-03-14 14:39:46: --> 250-8BITMIME
Fri 2008-03-14 14:39:46: --> 250-STARTTLS
Fri 2008-03-14 14:39:46: --> 250 SIZE 0
Fri 2008-03-14 14:39:46: <-- MAIL From:<xx@x.com> SIZE=56661
Fri 2008-03-14 14:39:46: Performing IP lookup (xx.com)
Fri 2008-03-14 14:39:46: *  D=xx.com TTL=(436) A=[x.x.x.x]
Fri 2008-03-14 14:39:47: *  P=010 S=000 D=xx.com TTL=(189) MX=[mail.x.com] {x.x.x.x}
Fri 2008-03-14 14:39:47: ---- End IP lookup results
Fri 2008-03-14 14:39:47: Performing SPF lookup (xx.com / x.x.x.x)
Fri 2008-03-14 14:39:47: *  xx.com x.x.x.x; matched to SPF cache
Fri 2008-03-14 14:39:47: *  Result: pass
Fri 2008-03-14 14:39:47: ---- End SPF results
Fri 2008-03-14 14:39:47: --> 250 <xx@x.com>, Sender ok
Fri 2008-03-14 14:39:47: <-- RCPT To:<xx@x.com>
Fri 2008-03-14 14:39:47: --> 451 Greylisting enabled, try again in 60 minutes
Fri 2008-03-14 14:39:47: <-- QUIT
Fri 2008-03-14 14:39:47: --> 221 See ya in cyberspace
Fri 2008-03-14 14:39:47: SMTP 会话终止（in/out 字节： 119/319）
Fri 2008-03-14 14:39:47: ----------
Fri 2008-03-14 14:39:55: Session 9851; child 3; thread 2712
Fri 2008-03-14 14:39:55: 接受 SMTP 连接来自 [x.x.x.x ：4014]
Fri 2008-03-14 14:39:55: Performing PTR lookup (x.x.x.x.IN-ADDR.ARPA)
Fri 2008-03-14 14:39:55: *  D=x.x.x.x.IN-ADDR.ARPA TTL=(932) PTR=[mail.x.com]
Fri 2008-03-14 14:39:55: *  Gathering A records...
Fri 2008-03-14 14:39:55: *  D=mail.x.com TTL=(112) A=[x.x.x.x]
Fri 2008-03-14 14:39:55: ---- End PTR results
Fri 2008-03-14 14:39:55: --> 220 x.com ESMTP MAIL ready
Fri 2008-03-14 14:39:55: <-- EHLO mail.x.com
Fri 2008-03-14 14:39:55: Performing IP lookup (mail.x.com)
Fri 2008-03-14 14:39:55: *  D=mail.x.com TTL=(112) A=[x.x.x.x]
Fri 2008-03-14 14:39:55: ---- End IP lookup results
Fri 2008-03-14 14:39:55: --> 250-x.com Hello mail.x.com, pleased to meet you
Fri 2008-03-14 14:39:55: --> 250-ETRN
Fri 2008-03-14 14:39:55: --> 250-AUTH=LOGIN
Fri 2008-03-14 14:39:55: --> 250-AUTH LOGIN CRAM-MD5
Fri 2008-03-14 14:39:55: --> 250-8BITMIME
Fri 2008-03-14 14:39:55: --> 250-STARTTLS
Fri 2008-03-14 14:39:55: --> 250 SIZE 0
Fri 2008-03-14 14:39:55: <-- MAIL From:<xx@x.com> SIZE=56661
Fri 2008-03-14 14:39:55: Performing IP lookup (xx.com)
Fri 2008-03-14 14:39:55: *  D=xx.com TTL=(436) A=[x.x.x.x]
Fri 2008-03-14 14:39:55: *  P=010 S=000 D=xx.com TTL=(189) MX=[mail.x.com] {x.x.x.x}
Fri 2008-03-14 14:39:55: ---- End IP lookup results
Fri 2008-03-14 14:39:55: Performing SPF lookup (xx.com / x.x.x.x)
Fri 2008-03-14 14:39:55: *  xx.com x.x.x.x; matched to SPF cache
Fri 2008-03-14 14:39:55: *  Result: pass
Fri 2008-03-14 14:39:55: ---- End SPF results
Fri 2008-03-14 14:39:55: --> 250 <xx@x.com>, Sender ok
Fri 2008-03-14 14:39:55: <-- RCPT To:<xx@x.com>
Fri 2008-03-14 14:39:55: --> 451 Greylisting enabled, try again in 60 minutes
Fri 2008-03-14 14:39:55: <-- QUIT
Fri 2008-03-14 14:39:55: --> 221 See ya in cyberspace
Fri 2008-03-14 14:39:55: SMTP 会话终止（in/out 字节： 119/319）
Fri 2008-03-14 14:39:55: ----------
Fri 2008-03-14 14:40:16: Session 9857; child 2; thread 2904
Fri 2008-03-14 14:40:15: 接受 SMTP 连接来自 [x.x.x.x ：4028]
Fri 2008-03-14 14:40:15: Performing PTR lookup (x.x.x.x.IN-ADDR.ARPA)
Fri 2008-03-14 14:40:15: *  D=x.x.x.x.IN-ADDR.ARPA TTL=(931) PTR=[mail.x.com]
Fri 2008-03-14 14:40:15: *  Gathering A records...
Fri 2008-03-14 14:40:15: *  D=mail.x.com TTL=(111) A=[x.x.x.x]
Fri 2008-03-14 14:40:15: ---- End PTR results
Fri 2008-03-14 14:40:15: --> 220 x.com ESMTP MAIL ready
Fri 2008-03-14 14:40:15: <-- EHLO mail.x.com
Fri 2008-03-14 14:40:15: Performing IP lookup (mail.x.com)
Fri 2008-03-14 14:40:15: *  D=mail.x.com TTL=(111) A=[x.x.x.x]
Fri 2008-03-14 14:40:15: ---- End IP lookup results
Fri 2008-03-14 14:40:15: --> 250-x.com Hello mail.x.com, pleased to meet you
Fri 2008-03-14 14:40:15: --> 250-ETRN
Fri 2008-03-14 14:40:15: --> 250-AUTH=LOGIN
Fri 2008-03-14 14:40:15: --> 250-AUTH LOGIN CRAM-MD5
Fri 2008-03-14 14:40:15: --> 250-8BITMIME
Fri 2008-03-14 14:40:15: --> 250-STARTTLS
Fri 2008-03-14 14:40:15: --> 250 SIZE 0
Fri 2008-03-14 14:40:16: <-- MAIL From:<xx@x.com> SIZE=56661
Fri 2008-03-14 14:40:16: Performing IP lookup (xx.com)
Fri 2008-03-14 14:40:16: *  D=xx.com TTL=(436) A=[x.x.x.x]
Fri 2008-03-14 14:40:16: *  P=010 S=000 D=xx.com TTL=(189) MX=[mail.x.com] {x.x.x.x}
Fri 2008-03-14 14:40:16: ---- End IP lookup results
Fri 2008-03-14 14:40:16: Performing SPF lookup (xx.com / x.x.x.x)
Fri 2008-03-14 14:40:16: *  xx.com x.x.x.x; matched to SPF cache
Fri 2008-03-14 14:40:16: *  Result: pass
Fri 2008-03-14 14:40:16: ---- End SPF results
Fri 2008-03-14 14:40:16: --> 250 <xx@x.com>, Sender ok
Fri 2008-03-14 14:40:16: <-- RCPT To:<xx@x.com>
Fri 2008-03-14 14:40:16: --> 451 Greylisting enabled, try again in 59 minutes
Fri 2008-03-14 14:40:16: <-- QUIT
Fri 2008-03-14 14:40:16: --> 221 See ya in cyberspace
Fri 2008-03-14 14:40:16: SMTP 会话终止（in/out 字节： 119/319）
Fri 2008-03-14 14:40:16: ----------
Fri 2008-03-14 14:40:26: Session 9859; child 2; thread 3384
Fri 2008-03-14 14:40:26: 接受 SMTP 连接来自 [x.x.x.x ：4045]
Fri 2008-03-14 14:40:26: Performing PTR lookup (x.x.x.x.IN-ADDR.ARPA)
Fri 2008-03-14 14:40:26: *  D=x.x.x.x.IN-ADDR.ARPA TTL=(931) PTR=[mail.x.com]
Fri 2008-03-14 14:40:26: *  Gathering A records...
Fri 2008-03-14 14:40:26: *  D=mail.x.com TTL=(111) A=[x.x.x.x]
Fri 2008-03-14 14:40:26: ---- End PTR results
Fri 2008-03-14 14:40:26: --> 220 x.com ESMTP MAIL ready
Fri 2008-03-14 14:40:26: <-- EHLO mail.x.com
Fri 2008-03-14 14:40:26: Performing IP lookup (mail.x.com)
Fri 2008-03-14 14:40:26: *  D=mail.x.com TTL=(111) A=[x.x.x.x]
Fri 2008-03-14 14:40:26: ---- End IP lookup results
Fri 2008-03-14 14:40:26: --> 250-x.com Hello mail.x.com, pleased to meet you
Fri 2008-03-14 14:40:26: --> 250-ETRN
Fri 2008-03-14 14:40:26: --> 250-AUTH=LOGIN
Fri 2008-03-14 14:40:26: --> 250-AUTH LOGIN CRAM-MD5
Fri 2008-03-14 14:40:26: --> 250-8BITMIME
Fri 2008-03-14 14:40:26: --> 250-STARTTLS
Fri 2008-03-14 14:40:26: --> 250 SIZE 0
Fri 2008-03-14 14:40:26: <-- MAIL From:<xx@x.com> SIZE=56661
Fri 2008-03-14 14:40:26: Performing IP lookup (xx.com)
Fri 2008-03-14 14:40:26: *  D=xx.com TTL=(435) A=[x.x.x.x]
Fri 2008-03-14 14:40:26: *  P=010 S=000 D=xx.com TTL=(189) MX=[mail.x.com] {x.x.x.x}
Fri 2008-03-14 14:40:26: ---- End IP lookup results
Fri 2008-03-14 14:40:26: Performing SPF lookup (xx.com / x.x.x.x)
Fri 2008-03-14 14:40:26: *  xx.com x.x.x.x; matched to SPF cache
Fri 2008-03-14 14:40:26: *  Result: pass
Fri 2008-03-14 14:40:26: ---- End SPF results
Fri 2008-03-14 14:40:26: --> 250 <xx@x.com>, Sender ok
Fri 2008-03-14 14:40:26: <-- RCPT To:<xx@x.com>
Fri 2008-03-14 14:40:26: --> 451 Greylisting enabled, try again in 59 minutes
Fri 2008-03-14 14:40:26: <-- QUIT
Fri 2008-03-14 14:40:26: --> 221 See ya in cyberspace
Fri 2008-03-14 14:40:26: SMTP 会话终止（in/out 字节： 119/319）
Fri 2008-03-14 14:40:33: Session 9863; child 2; thread 1604
Fri 2008-03-14 14:40:33: 接受 SMTP 连接来自 [x.x.x.x ：4062]
Fri 2008-03-14 14:40:33: Performing PTR lookup (x.x.x.x.IN-ADDR.ARPA)
Fri 2008-03-14 14:40:33: *  D=x.x.x.x.IN-ADDR.ARPA TTL=(931) PTR=[mail.x.com]
Fri 2008-03-14 14:40:33: *  Gathering A records...
Fri 2008-03-14 14:40:33: *  D=mail.x.com TTL=(111) A=[x.x.x.x]
Fri 2008-03-14 14:40:33: ---- End PTR results
Fri 2008-03-14 14:40:33: --> 220 x.com ESMTP MAIL ready
Fri 2008-03-14 14:40:33: <-- EHLO mail.x.com
Fri 2008-03-14 14:40:33: Performing IP lookup (mail.x.com)
Fri 2008-03-14 14:40:33: *  D=mail.x.com TTL=(111) A=[x.x.x.x]
Fri 2008-03-14 14:40:33: ---- End IP lookup results
Fri 2008-03-14 14:40:33: --> 250-x.com Hello mail.x.com, pleased to meet you
Fri 2008-03-14 14:40:33: --> 250-ETRN
Fri 2008-03-14 14:40:33: --> 250-AUTH=LOGIN
Fri 2008-03-14 14:40:33: --> 250-AUTH LOGIN CRAM-MD5
Fri 2008-03-14 14:40:33: --> 250-8BITMIME
Fri 2008-03-14 14:40:33: --> 250-STARTTLS
Fri 2008-03-14 14:40:33: --> 250 SIZE 0
Fri 2008-03-14 14:40:33: <-- MAIL From:<xx@x.com> SIZE=56661
Fri 2008-03-14 14:40:33: Performing IP lookup (xx.com)
Fri 2008-03-14 14:40:33: *  D=xx.com TTL=(435) A=[x.x.x.x]
Fri 2008-03-14 14:40:33: *  P=010 S=000 D=xx.com TTL=(189) MX=[mail.x.com] {x.x.x.x}
Fri 2008-03-14 14:40:33: ---- End IP lookup results
Fri 2008-03-14 14:40:33: Performing SPF lookup (xx.com / x.x.x.x)
Fri 2008-03-14 14:40:33: *  xx.com x.x.x.x; matched to SPF cache
Fri 2008-03-14 14:40:33: *  Result: pass
Fri 2008-03-14 14:40:33: ---- End SPF results
Fri 2008-03-14 14:40:33: --> 250 <xx@x.com>, Sender ok
Fri 2008-03-14 14:40:33: <-- RCPT To:<xx@x.com>
Fri 2008-03-14 14:40:33: --> 451 Greylisting enabled, try again in 59 minutes
Fri 2008-03-14 14:40:33: <-- QUIT
Fri 2008-03-14 14:40:33: --> 221 See ya in cyberspace
Fri 2008-03-14 14:40:33: SMTP 会话终止（in/out 字节： 119/319）
Fri 2008-03-14 14:40:33: ----------
Fri 2008-03-14 14:40:53: Session 9867; child 3; thread 608
Fri 2008-03-14 14:40:52: 接受 SMTP 连接来自 [x.x.x.x ：4085]
Fri 2008-03-14 14:40:52: Performing PTR lookup (x.x.x.x.IN-ADDR.ARPA)
Fri 2008-03-14 14:40:52: *  D=x.x.x.x.IN-ADDR.ARPA TTL=(931) PTR=[mail.x.com]
Fri 2008-03-14 14:40:52: *  Gathering A records...
Fri 2008-03-14 14:40:52: *  D=mail.x.com TTL=(111) A=[x.x.x.x]
Fri 2008-03-14 14:40:52: ---- End PTR results
Fri 2008-03-14 14:40:52: --> 220 x.com ESMTP MAIL ready
Fri 2008-03-14 14:40:52: <-- EHLO mail.x.com
Fri 2008-03-14 14:40:52: Performing IP lookup (mail.x.com)
Fri 2008-03-14 14:40:52: *  D=mail.x.com TTL=(111) A=[x.x.x.x]
Fri 2008-03-14 14:40:52: ---- End IP lookup results
Fri 2008-03-14 14:40:52: --> 250-x.com Hello mail.x.com, pleased to meet you
Fri 2008-03-14 14:40:52: --> 250-ETRN
Fri 2008-03-14 14:40:52: --> 250-AUTH=LOGIN
Fri 2008-03-14 14:40:52: --> 250-AUTH LOGIN CRAM-MD5
Fri 2008-03-14 14:40:52: --> 250-8BITMIME
Fri 2008-03-14 14:40:52: --> 250-STARTTLS
Fri 2008-03-14 14:40:52: --> 250 SIZE 0
Fri 2008-03-14 14:40:53: <-- MAIL From:<xx@x.com> SIZE=56661
Fri 2008-03-14 14:40:53: Performing IP lookup (xx.com)
Fri 2008-03-14 14:40:53: *  D=xx.com TTL=(435) A=[x.x.x.x]
Fri 2008-03-14 14:40:53: *  P=010 S=000 D=xx.com TTL=(188) MX=[mail.x.com] {x.x.x.x}
Fri 2008-03-14 14:40:53: ---- End IP lookup results
Fri 2008-03-14 14:40:53: Performing SPF lookup (xx.com / x.x.x.x)
Fri 2008-03-14 14:40:53: *  xx.com x.x.x.x; matched to SPF cache
Fri 2008-03-14 14:40:53: *  Result: pass
Fri 2008-03-14 14:40:53: ---- End SPF results
Fri 2008-03-14 14:40:53: --> 250 <xx@x.com>, Sender ok
Fri 2008-03-14 14:40:53: <-- RCPT To:<xx@x.com>
Fri 2008-03-14 14:40:53: --> 451 Greylisting enabled, try again in 59 minutes
Fri 2008-03-14 14:40:53: <-- QUIT
Fri 2008-03-14 14:40:53: --> 221 See ya in cyberspace
Fri 2008-03-14 14:40:53: SMTP 会话终止（in/out 字节： 119

默认要禁60分钟，并且不知道为什么选择了不GREY通过SPF处理的邮件还是会被列，看来此功能还是应慎用。

dennishan

灰地址就是延迟邮件到达，默认要第二次发送过来的邮件才批准，第一次就暂时断开。
目的是阻止那些没有队列的垃圾邮件。

如果垃圾发送者连续发送2次，灰地址就失效了。
灰地址的缺点：可能引起正常邮件延迟到达。

wxhsh

但MD默认不是次数判断，而是分钟，默认60分钟内任意尝试都被拒绝的，这个延迟厉害了，并且不同邮局还有重试次数设置，如果超过了一定次数那延迟更厉害了，可能要第二天才能收到。

钉子

我个人认为MD将灰名单时间默认时间设为60分钟并不合适，一般5-10分钟即可。不然就会延迟太严重了。一般正常的邮件系统第二次重试的队列也不会短于5分钟的。这样也利于节约服务器资源。