我在 Exchange 2007 的队列视图中看到不少“421 4.4.2 连接断开”错误。我已验证 rDNS 等设置正确。我已重新启动。并非所有域都存在此问题，只有少数几个。
当我查看数据包时，我从 SMTP 服务器收到的最后一条命令是“SMTP 服务器就绪”
174.47.59.19 172.16.2.178 SMTP SMTP:Rsp 220 mail.ntgrated.com Microsoft ESMTP MAIL Service, Version: 6.0.3790.3959 ready at Thu, 15 Mar 2012 09:58:11 -0500 , 119 bytes
172.16.2.178 174.47.59.19 SMTP SMTP:Cmd EHLO mail.serviceprovidergroup.com, 36 bytes
174.47.59.19 172.16.2.178 SMTP SMTP:Rsp 250 -mail.ntgrated.com Hello [69.128.140.103], 334 bytes
172.16.2.178 174.47.59.19 SMTP SMTP:Cmd STARTTLS, Server is currently able to negotiate the use of TLS
174.47.59.19 172.16.2.178 SMTP SMTP:Rsp 220 2.0.0 SMTP server ready, 29 bytes
174.47.59.19 172.16.2.178 SMTP SMTP:Rsp 220 mail.ntgrated.com Microsoft ESMTP MAIL Service, Version: 6.0.3790.3959 ready at Thu, 15 Mar 2012 09:58:12 -0500 , 119 bytes
172.16.2.178 174.47.59.19 SMTP SMTP:Cmd EHLO mail.serviceprovidergroup.com, 36 bytes
174.47.59.19 172.16.2.178 SMTP SMTP:Rsp 250 -mail.ntgrated.com Hello [69.128.140.103], 334 bytes
172.16.2.178 174.47.59.19 SMTP SMTP:Cmd STARTTLS, Server is currently able to negotiate the use of TLS
174.47.59.19 172.16.2.178 SMTP SMTP:Rsp 220 2.0.0 SMTP server ready, 29 bytes
当比较到达另一个域名的电子邮件时，我看到了完整的通信内容：
172.16.2.178 69.128.140.110 SMTP SMTP:Rsp 220 mail.serviceprovidergroup.com Microsoft ESMTP MAIL Service ready at Thu, 15 Mar 2012 11:00:31 -0400, 105 bytes
69.128.140.110 172.16.2.178 SMTP SMTP:Cmd EHLO se-10-1-10-1.localdomain, 31 bytes
172.16.2.178 69.128.140.110 SMTP SMTP:Rsp 250 -mail.serviceprovidergroup.com Hello [69.128.140.110], 191 bytes
69.128.140.110 172.16.2.178 SMTP SMTP:Cmd MAIL FROM:<do-not-reply@localdomain>, 38 bytes
172.16.2.178 69.128.140.110 SMTP SMTP:Rsp 250 2.1.0 Sender OK, 21 bytes
69.128.140.110 172.16.2.178 SMTP SMTP:Cmd RCPT TO:<[email protected]>, 46 bytes
172.16.2.178 69.128.140.110 SMTP SMTP:Rsp 250 2.1.5 Recipient OK, 24 bytes
69.128.140.110 172.16.2.178 SMTP SMTP:Cmd DATA, Begins message composition
172.16.2.178 69.128.140.110 SMTP SMTP:Rsp 354 Start mail input; end with <CRLF>.<CRLF>, 46 bytes
69.128.140.110 172.16.2.178 SMTP SMTP:Data Payload, 1448 bytes
...
69.128.140.110 172.16.2.178 SMTP SMTP:Data Payload, 107 bytes
172.16.2.178 69.128.140.110 SMTP SMTP:Rsp 250 2.6.0 <[email protected]> Queued mail for delivery, 100 bytes
69.128.140.110 172.16.2.178 SMTP SMTP:Cmd QUIT, Terminates the mail session
172.16.2.178 69.128.140.110 SMTP SMTP:Rsp 221 2.0.0 Service closing transmission channel, 48 bytes
我可以通过 telnet 连接到这些域并全天手动执行命令，并且它能够通过，但只有在 Exchange 中发送时才可以。
当我们在本周末升级 Fortigate 防火墙时，这个问题开始出现，但我找不到任何可能导致这些问题的原因。
使用 ping（除非有更好的方法）我已经确认两者之间没有丢失数据包。
谢谢