Update dkim_dmarc_spf.md

Co-authored-by: Brennan Kinney <5098581+polarathene@users.noreply.github.com>
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Georg Lauterbach 2024-06-18 16:02:10 +02:00 committed by GitHub
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@ -38,7 +38,7 @@ DKIM requires a public/private key pair to enable **signing (_via private key_)*
Unlike your TLS certificate, your DKIM keypair does not have a fixed expiry associated to it. Unlike your TLS certificate, your DKIM keypair does not have a fixed expiry associated to it.
Instead an expiry may be included in your DKIM signature for each mail sent, where a receiver will [refuse to validate the signature for an email after that expiry date][dkim-verification-expiry-refusal]. This is an added precaution to mitigate malicious activity like "DKIM replay attacks", where a trustworthy DKIM signature from an existing mail from a third-party is recycled to enable a spammer to bypass security precautions. Instead an expiry may be included in your DKIM signature for each mail sent, where a receiver will [refuse to validate the signature for an email after that expiry date][dkim-verification-expiry-refusal]. This is an added precaution to mitigate malicious activity like "DKIM replay attacks", where an already delivered email from a third-party with a trustworthy DKIM signature is leveraged by a spammer when sending mail to an MTA which verifies the DKIM signature successfully, enabling the spammer to bypass spam protections.
Unlike a TLS handshake where you are authenticating trust with future communications, with DKIM once the mail has been received and trust of the signature has been verified, the value of verifying the signature again at a later date is less meaningful since the signature was to ensure no tampering had occurred during delivery through the network. Unlike a TLS handshake where you are authenticating trust with future communications, with DKIM once the mail has been received and trust of the signature has been verified, the value of verifying the signature again at a later date is less meaningful since the signature was to ensure no tampering had occurred during delivery through the network.