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DomainKeys Identified Mail (DKIM) is an email authentication method designed to detect forged sender addresses in email (email spoofing), a technique often used in phishing and email spam.
DKIM allows the receiver to check that an email that claimed to have come from a specific domain was indeed authorized by the owner of that domain.[1] It achieves this by affixing a digital signature, linked to a domain name, to each outgoing email message. The recipient system can verify this by looking up the sender's public key published in the DNS. A valid signature also guarantees that some parts of the email (possibly including attachments) have not been modified since the signature was affixed.[2] Usually, DKIM signatures are not visible to end-users, and are affixed or verified by the infrastructure rather than the message's authors and recipients.
DKIM is an Internet Standard.[3] It is defined in RFC 6376, dated September 2011, with updates in RFC 8301 and RFC 8463.
Receivers who successfully verify a signature can use information about the signer as part of a program to limit spam, spoofing, phishing, or other undesirable behaviors. DKIM does not, itself, prescribe any specific actions by the recipient; rather, it is an enabling technology for services that do.
Verifying the signature asserts that the hashed content has not changed since it was signed and asserts nothing else about "protecting" the end-to-end integrity of the message.