有没有一种方法，我可以告诉一个SMTP服务器是否正在期待一个客户端使用＆QUOT进行连接;隐＆QUOT; SSL与＆QUOT;明确＆QUOT; SSL？ [英] Is there a way I can tell whether an SMTP server is expecting a client to connect using "implicit" SSL versus "explicit" SSL?

问题描述

通过这个链接所解释的SSL可以是明确的或隐：

SSL can either be "explicit" or "implicit" as explained by this link:

的http://help.globalscape.com/help/secureserver2/Explicit_versus_implicit_SS.htm

System.Net.Mail只支持明确的SSL，如下解释：

System.Net.Mail only support "explicit" SSL, as explained here:

<一个href="http://blogs.msdn.com/webdav_101/archive/2008/06/02/system-net-mail-with-ssl-to-authenticate-against-port-465.aspx" rel="nofollow">http://blogs.msdn.com/webdav_101/archive/2008/06/02/system-net-mail-with-ssl-to-authenticate-against-port-465.aspx

所以，我试图用System.Net.Mail连接到我没有任何控制权的SMTP服务器，它的失败。我怎么能肯定知道，它的失败，因为服务器需要一个隐SSL连接？我可以从客户端做些什么测试？

So, I'm trying to use System.Net.Mail to connect to an SMTP server that I don't have any control over, and it's failing. How can I know for sure that it's failing because the server wants an "implicit" SSL connection? What test can I do from the client side?

推荐答案

通常这是由公约管辖。 SMTP端口25（正常情况下）运行使用显式的SSL。 SMTPS端口465上运行使用隐式SSL。邮件提交端口587上运行使用显式的SSL。

Ordinarily this is governed by convention. SMTP running on port 25 (the normal case) uses explicit SSL. SMTPS running on port 465 uses implicit SSL. Mail submission running on port 587 uses explicit SSL.

要肯定地告诉，telnet到端口，如远程登录mail.example.com 25。如果你看到的服务器标识本身就是一个纯文本的旗帜，那么你正在处理的明确SSL。如果连接成功后什么也看不见，那么你正在处理隐含的SSL。

To tell for sure, telnet to the port, as in "telnet mail.example.com 25". If you see a plain text banner where the server identifies itself, then you are dealing with explicit SSL. If you connect successfully and see nothing, then you are dealing with implicit SSL.

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