【正文】 S: 504 unrecognized authentication types.C: AUTH CRAMMD5S: 235 Authentication successful.5. The AUTH parameter to the MAIL FROM mandAUTH=addrspecArguments:An addrspec containing the identity which submitted the message to the delivery system, or the two character sequence , indicating such an identity is unknown or insufficiently authenticated.Discussion:The optional AUTH parameter to the MAIL FROM mand allows cooperating agents in a trusted environment to municate the authentication of individual messages.If the server trusts the authenticated identity of the client toAssert that the message was originally submitted by the supplied addrspec, and then the server SHOULD supply the same addrspec in an AUTH parameter when relaying the message to any server which supports the AUTH extension.A MAIL FROM parameter of AUTH= indicates that the original submitter of the message is not known. The server MUST NOT treat the message as having been originally submitted by the client. If the AUTH parameter to the MAIL FROM is not supplied, the client has authenticated, and the server believes the message is an original submission by the client, the server MAY supply the client39。 second is from one server to another server. SMTP is a request / response protocol, it listen port 25, for receiving the user39。外文資料原文SMTP Service Extension for AuthenticationRFC 2554This document specifies an Internet standards track protocol for the Internet munity, and requests discussion and suggestions for improvements. Please refer to the current edition of the Internet Official Protocol Standards (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.There are usually two operating modes: SMTP to send and receive SMTP. Specific way: to send SMTP mail in the received user request to determine whether this local mail, if sent to the user39。s Mail request to establish with the remote Mail server SMTP connection.Copyright NoticeCopyright (C) the Internet Society (1999). All Rights Reserved.1. IntroductionThis document defines an SMTP service extension [ESMTP] whereby an SMTP client may indicate an authentication mechanism to the server。s identity in the addrspec in an AUTH parameter when relaying the message to any server which supports the AUTH extension.If the server does not sufficiently trust the authenticated identity of the client, or if the client is not authenticated, then the server MUST behave as if the AUTH= parameter was supplied. The server MAY, however, write the value of the AUTH parameter to a log file.If an AUTH= parameter was supplied, either explicitly or due to the requirement in the previous paragraph, then the server MUST supply the AUTH= parameter when relaying the message to any server which it has authenticated to using the AUTH extension.A server MAY treat expansion of a mailing list as a new submission, setting the AUTH parameter to the mailing list address or mailing list administration address when relaying the message to list subscribers.It is conforming for an implementation to be hardcoded to treat all clients as being insufficiently trusted. In that case, the implementation does nothing more than parse and discard syntactically valid AUTH parameters to the MAIL FROM mand and supply AUTH= parameters to any servers to which it authenticates using the AUTH extension.Examples:C: MAIL FROM : e=mc2 AUTH=e+3Dmc2S: 250 OK6. Error CodesThe following error codes may be used to indicate various conditions as described.432 A password transition is neededThis response to the AUTH mand indicates that the user needs to transition to the selected authentication mechanism. This typically done by authenticating that once using the PLAIN authentication Authentication mechanisms is too weak.This response to the AUTH mand indicates that the selected authentication mechanism is weaker than server policy permits for that user.538 Encryption required for requested authentication mechanismThis response to the AUTH mand indicates that the selected authentication mechanism may only be used when the underlying SMTP connection is encrypted.454 Temporary authentication failuresThis response to the AUTH mand indicates that the authentication failed due to a temporary server failure.530 Authentication requiredThis response may be returned by any mand other than AUTH, EHLO, HELO, NOOP, RSET, or QUIT. It indicates that server policy requires authentication in order to perform the requested action.7. Formal SyntaxThe following syntax specification uses the augmented BackusNaur Form (BNF) notation as specified in [ABNF].Except as noted otherwise, all alphabetic characters are case insensitive. The use of upper o