我在我的sendmail日志中注意到了以下内容:
May 11 11:11:16 foobox sendmail[21111]: uADEFHG21111: [1.1.1.1]: probable open proxy: command=POST http://foo2.example.com
May 11 11:11:16 foobox sendmail[21111]: uADEFHG21111: [1.1.1.1] did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA
(IP、QID 和日期已更改以保护无辜者:-))
以下是另外几个错误:
May 11 12:12:12 foobox sendmail[22222]: u4BACDCDC22222: [1.1.1.1]: probable open proxy: command=GET http://example2.domain.com/foo2/
May 11 12:12:12 foobox sendmail[22222]: u4BACDCDC22222: [1.1.1.1] did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA
我以前从未见过这种情况,我不清楚这里到底发生了什么。有人能详细说明一下吗?是否有东西试图通过网络连接启动 SMTP 连接?或者反之亦然?
答案1
Sendmail 认为连接“很可能”是通过开放的 http 代理进行的。从垃圾邮件预防的角度来看,发送标准的“无法识别的命令”回复并接受下一个 SMTP 命令是“不明智的”。[它在]
中实现srvrsmtp.c
HTTP 代理服务器可能会发送/中继嵌入 HTTP 请求的有效 SMTP 命令。如果没有此改进,则可能导致无法接受电子邮件消息,尤其是无法接收本地邮箱的电子邮件消息。
我认为它已经不像以前那么有用了但距离从 sendmail 的代码中删除还很远。
sendmail 的RELEASE_NOTES
文件:
8.14.0/8.14.0 2007/01/31
....
Try to deal with open HTTP proxies that are used to send spam
by recognizing some commands from them. If the first command
from the client is GET, POST, CONNECT, or USER, then the
connection is terminated immediately.