What must be provided for DNS records during the sending domain validation process?

During the sending domain validation process, a unique validation key is required in order to confirm that you have control over the domain from which you intend to send emails. This key is typically provided by the email service provider and must be added to the DNS records of your domain. The presence of this unique validation key in the DNS confirms ownership and ensures that only authorized individuals can send emails on behalf of that domain.

The other options do not pertain to the specific requirements for DNS records in the validation process. A previous registration date, for instance, is irrelevant to the verification of domain ownership. Similarly, a data usage report or a list of previous domains does not assist in validating the sending domain for email campaigns. Thus, the unique validation key is the essential element for establishing that you have the rights to the domain, making it the correct choice in this scenario.