下面的例子是用139的smtp伺服器

telnet smtp.139.com 25     //telnet到smtp埠
Trying 120.232.169.42...
Connected to smtp.139.com.
Escape character is '^]'.
220 localhost richmail system v10(2f176279184726f-809c0) //伺服器返回220
helo mytest     //跟伺服器打招呼
250 localhost richmail system v10(2f176279184726f-809c0)  //伺服器返回250
auth login    //登入
 

334 dXNlcm5hbWU6 //伺服器返回334
*** //*此處輸入base64編碼後的qq郵箱名*/
334 UGFzc3dvcmQ6 //伺服器返回334
*** //*此處輸入base64編碼後的授權碼*/
235 Authentication successful  //登入成功
mail from: <kfwtry@139.com>  //發件郵箱
250 ok
rcpt to: <[email protected]>  //收件郵箱
250 ok
data    //開始寫信
354 end with .
to:hello    //郵件收件人的名稱
from:mytest    //郵件來源名稱
subject: this
 
 is a test telnet smtp mail    //郵件標題
hello,my friend        //訊息內容
  This is a test mail form 139.com       //訊息內容
.   //英文的點，郵件結束標誌。即刻傳送

 Base64線上編碼/解碼  https://base64.us/