Domain Keys Identified Mail
charter-ietf-dkim-04-00

Domain Keys Identified Mail (DKIM, RFC 6376) defines a mechanism for
using a digital signature to associate a domain identity with an email
message in a secure way, and to assure receiving domains that the message has
not been altered since the signature was created. Receiving systems
can use this information as part of their message-handling decision.
This can help reduce spam, phishing, and other unwanted or malicious
email.

A DKIM-signed message can be re-posted, to additional recipients, in a
fashion that retains the original signature. With an author and a recipient
collaborating, this can "replay" the message, using the original signer's
reputation to propagate email with problematic content -- spam, phishing,
and the like.

Generally, the technical characteristics of this form of abuse match that of
legitimate mail, making its detection or prevention challenging. Timestamps
and carefully-tailored message signing conventions are appealing approaches
to replay mitigation. Each has significant limitations.

The DKIM working group will produce one or more technical specifications that
describe the abuse and propose replay-resistant mechanisms. The working group will
seek compatibility with DKIM's broad deployment.

Current proposals include the following drafts:

- draft-bradshaw-envelope-validation-extension-dkim
 - draft-chuang-replay-resistant-arc
 - draft-gondwana-email-mailpath
 - draft-kucherawy-dkim-anti-replay

The working group may adopt or ignore these as it sees fit.