DKIM ADSP

The add-on to DKIM

!DomainKeys Identified Mail (DKIM) defines a domain-level authentication framework for email to permit verification of the source and contents of messages. ADSP specifies an adjunct mechanism to aid in assessing messages that do not contain a DKIM signature for the domain used in the author’s address. It defines a DNS TXT RR record that can advertise whether a domain signs its outgoing mail as well as how other hosts can access that record.

 _adsp._domainkey.<domain_name> IN TXT "dkim=<practice>

where <practice> can be:

• unknown - The domain might sign some or all email.
• all - All mail from the domain is signed with an Author Domain Signature.
• discardable - All mail from the domain is signed with an Author Domain Signature. Furthermore, if a message arrives without a valid Author Domain Signature due to modification in transit, submission via a path without access to a signing key, or any other reason, the domain encourages the recipient(s) to discard it.