研究郵件透明加密技術時，用到了imap協議，使用telnet作為測試和學習imap協議很不錯，現總結如下:
1、登錄郵件服務器,imap協議端口是143
telnet imap.163.com 143
2、輸入標簽號，標簽號在整個連接中要保持唯一。然后輸入賬戶名和密碼。
A0001 login laoww@163.com 123456
3、輸入標簽號，使用select選中收件箱inbox
A0002 select inbox
4、搜索收件箱中所有未刪除的郵件
A0003 UID SEARCH UNDELETED
5、輸入fetch指令下載制定uid的郵件
A0004 UID FETCH 3 (BODY.PEEK[HEADER.FIELDS (CONTENT-TRANSFER-ENCODING CONTENT-TYPE X-SECIV X-SECKEY X-Mailer X-Tyin)])
以下指令是獲取郵件各個部分的指令:
a0008 UID FETCH 3 (BODY.PEEK[HEADER.FIELDS (CONTENT-TRANSFER-ENCODING CONTENT-TYPE X-SECIV X-SECKEY)])
a0018 UID FETCH 3 (BODY[HEADER.FIELDS (MESSAGE-ID CONTENT-TRANSFER-ENCODING CONTENT-TYPE X-Seciv X-Seckey X-Mailer X-Alimail-AntiSpam)])
a0015 UID FETCH 3 (BODY.PEEK[HEADER])
a0016 UID FETCH 3 (BODY[HEADER])
a2004 UID FETCH 112 RFC822.HEADER
A0006 UID FETCH 40 (BODY.PEEK[0.MIME])
A0006 UID FETCH 3 (BODY.PEEK[])
最后介紹一下郵件透明加密，目前市場上有很多郵件加密產品，但是透明加密產品卻很少。郵件透明加密主要優點是部署簡單，用戶無感知。其中天御雲安的隱密郵，在透明加密方面做的很好。百聞不如一見，網址是：https://mail.tyyunan.com/