SMTP command line

SMTP command line

2008/08/24 10:45

Define the process of the SMTP protocol, and write a mail-sending program accordingly. 1. SMTP SMTP (Simple Mail Transfer Protocol): A transport protocol used by e-mail messages to transfer from a client to a server or from one server to another server. SMTP is a request/response protocol in which commands and responses are based on ASCII text and end with CR and LF. The response includes a three-bit numeric code that represents the return status. SMTP listens for connection requests on TCP protocol 25 ports. What is ESMTP ESMTP (Extended SMTP), as the name suggests, extends SMTP as an extension of the standard SMTP protocol. It differs from the SMTP service simply by using SMTP to send letters without authenticating user accounts, and when sending a letter with ESMTP, the server asks the user for a username and password to authenticate. The message delivery process after validation is no different from the SMTP method. 2.ESMTP ESMTP (Extended SMTP), as the name suggests, extends SMTP as an extension of the standard SMTP protocol. It differs from the SMTP service simply by using SMTP to send letters without authenticating user accounts, and when sending a letter with ESMTP, the server asks the user for a username and password to authenticate. The message delivery process after validation is no different from the SMTP method. 3.SMTP command HELO identifies the user identity to the server. The sender can cheat, lie, but in general the server can detect. EHLO identifies the user identity to the server. The sender can cheat, lie, but in general the server can detect. The address specified in the MAIL from command is the sender's address RCPT to identifies a single message recipient; multiple RCPT to; often behind mail commands. After a single or multiple RCPT command, data indicates that all recipients of the message have identified and initialized the data transfer to CRLF. CRLF End VRFY is used to verify that the specified user/mailbox exists or that the server often prohibits this command for security reasons EXPN Verify that a given mailbox list exists, and that the expanded mailbox list is often disabled Help query server What commands are supported NOOP no action, server should respond OK RSET reset session, current transfer canceled QUIT End Session 4. Command line Letter Process Microsoft Windows XP [version 5.1.2600] (C) Copyright 1985-2001 Microsoft Corp. C:\Documents and Settings\administrator>telnet Welcome to the Microsoft Telnet Client Escape character is ' Ctrl +] ' Microsoft Telnet>open smtp.sohu.com 25 Smtp.sohu.com ESMTP Postfix > Helo 250-smtp.sohu.com 250-pipelining 250-size 10240000 250-vrfy 250-etrn 250-auth LOGIN 250-enhancedstatuscodes 250-8bitmime A DSN > Auth Login 334 Vxnlcm5hbwu6 > z2fvbwfuewlac29ods5jb20= #Base64Encode (gaomanyi@sohu.com) = z2fvbwfuewlac29ods5jb20= 334 Ugfzc3dvcmq6 > **************** #Base64Encode (Password) =this is a secret! 235 2.0.0 Authentication Successful > Mail from:<gaomanyi@sohu.com> 2.1.0 Ok RCPT to:<gamma.gao@hotmail.com> 2.1.5 Ok Data 354 End data with <CR><LF>.<CR><LF> Date:sun, Aug 2008 11:03:27 +0800 #随便假定个时间 From:<gaomanyi@sohu.com> To:<gamma.gao@sohu.com> #故意写错 Subject:test for SMTP command This is my test! . 2.0.0 ok:queued as 75f228e8774 Quit 221 2.0.0 Bye OK, got the letter, the situation is this: --- Test for SMTP command #主题正确 Sender: Gaomanyi@sohu.com Send time: August 24, 2008 11:04:43 #时间得到更正 Recipient: gamma.gao@sohu.com #收件人没更正过来, Silly x This is my test!