Constant Contact

Constant Contact's self-authentication tutorial directs senders to add the DNS records Constant Contact generates for the domain, including DKIM CNAME records Constant Contact can rotate on the sender's behalf.

Constant Contact's community authentication guide says senders who control their own domain should use self-authentication and publish the records Constant Contact displays. Yahoo and Google bulk-sender policy changes are cited there as reasons to authenticate domains that send marketing mail.

Records from the account

Constant Contact's knowledge base article on self-authentication is the starting point for copying hostnames and targets into the DNS provider. Values are tied to the Constant Contact account and domain being authenticated.

After DKIM verifies, Constant Contact's materials describe DMARC as a separate TXT policy at _dmarc. RFC 7489 defines that record; Constant Contact's UI generates the authentication records for DKIM alignment.

Self-authentication

Constant Contact's knowledge base tutorial is the canonical source for hostnames and targets to paste into DNS.

Constant Contact's community authentication guide recommends self-authentication when you control the sending domain.

DMARC remains a separate _dmarc TXT under RFC 7489 after DKIM records verify.

What is DKIM
DKIM signs a message. The public key is a TXT record under _domainkey. The signature's s= tag is the selector and d= is the signing domain.
What is DMARC
DMARC is a TXT record at _dmarc plus the domain. It tells the receiver what to do when the From address is not aligned with a passing SPF or DKIM result, and where to send the reports.
Mailchimp
Mailchimp's domain-authentication help asks for two DKIM CNAME records and one DMARC TXT record at _dmarc when you authenticate manually. The values are copied from the Domains page in the Mailchimp account.