Editing Email testing (section)

== For role: system administrator ==
If you have the telnet permission,
* Suggest search keyword: [http://lmgtfy.com/?q=smtp%20telnet%20test smtp telnet test]
* [https://technet.microsoft.com/zh-tw/library/aa995718(v=exchg.65).aspx 如何使用 Telnet 來測試 SMTP 通訊]
* [https://support.google.com/mail/answer/78775?hl=zh-Hant 使用 POP 或 IMAP 傳送郵件時發生問題 - Gmail說明] {{access | date = 2016-08-08}}
* [http://www.xspace.idv.tw/bo_blog/post/85/ Outlook 錯誤代碼的含義及解決辦法] {{access | date = 2016-12-22}}

是否可以連線到 SMTP 主機{{kbd | key =<nowiki>nslookup smtp.gmail.com</nowiki> }} 或 {{kbd | key =<nowiki>telnet smtp.gmail.com port</nowiki> }} (例子中以 gmail 作為 smtp 伺服器)
{{kbd | key =<nowiki>telnet smtp.gmail.com 465</nowiki> }} 預期結果：
<pre>
Trying 74.125.129.109...
Connected to smtp.gmail.com.
Escape character is '^]'.
^] //註：(Windows) 輸入 ctrl + ] 兩個按鍵，(Mac) 輸入 control + ] 兩個按鍵
telnet> quit
Connection closed.
</pre>

非預期結果：請調整防火牆設定
<pre>
Trying x.x.x.x...
telnet: connect to address x.x.x.x: Connection refused
</pre>