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DomainKeys Identified Mail (DKIM) is an email validation system designed to detect email spoofing by providing a mechanism to allow receiving mail exchangers to check that incoming mail from a domain is authorized by that domain's administrators and that the email (including attachments) has not been modified during transport. A digital signature included with the message can be validated by the recipient using the signer's public key published in the DNS. In technical terms, DKIM is a technique to authorize the domain name which is associated with a message through cryptographic authentication. DKIM is the result of merging DomainKeys and Identified Internet Mail. This merged specification has been the basis for a series of IETF standards-track specifications and support documents which eventually resulted in STD (76 ) (aka RFC 6376). Prominent email service providers implementing DKIM include Yahoo, Gmail, AOL and FastMail. Any mail from these organizations should carry a DKIM signature.〔Delany, Mark (May 22, 2007). ("One small step for email, one giant leap for Internet safety" ). Yahoo! corporate blog. Delany is credited as Chief Architect, inventor of DomainKeys.〕〔Taylor, Brad (July 8, 2008). ("Fighting phishing with eBay and Paypal" ). Gmail Blog.〕〔("I’m having trouble sending messages in Gmail" ). Gmail Help entry, mentioning DKIM support when sending.〕〔Mueller, Rob (August 13, 2009). ("All outbound email now being DKIM signed" ). Fastmail blog.〕 == Overview == Both modules, signing and verifying, are usually part of a mail transfer agent (MTA). The signing organization can be a direct handler of the message, such as the author, the originating sending site or an intermediary along the transit path, or an indirect handler such as an independent service that is providing assistance to a direct handler. In most cases, the signing module acts on behalf of the author organization or the originating service provider by inserting a DKIM-Signature: header field. The verifying module typically acts on behalf of the ''receiver'' organization. The need for this type of validated identification arose because spam often has forged addresses and content. For example, a spam message may claim in its "From:" header field to be from sender@example.com, although it is not actually from that address or domain or entity, and the spammer's goal is to convince the recipient to accept and to read the email. It is difficult for recipients to establish whether to trust or distrust any particular message or even domain, and system administrators may have to deal with complaints about spam that appears to have originated from their systems but did not. DKIM is independent of Simple Mail Transfer Protocol (SMTP) routing aspects in that it operates on the RFC 5322 message—the transported mail's header and body—not the SMTP envelope defined in RFC 5321. Hence the DKIM signature survives basic relaying across multiple MTAs. DKIM allows the signer to distinguish its legitimate mail stream. It does not directly prevent or disclose abusive behavior. This ability to distinguish legitimate mail from potentially forged mail has benefits for recipients of e-mail as well as senders, and "DKIM awareness" is programmed into some e-mail software. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「DomainKeys Identified Mail」の詳細全文を読む スポンサード リンク
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