Which encryption method allows email verification through a digital signature?

The correct choice involves DKIM, or DomainKeys Identified Mail, which is a method specifically designed for email verification through the use of digital signatures. DKIM works by adding a cryptographic signature to the header of an email message. This signature is generated using a private key that only the sender’s mail server possesses. When the email is received, the recipient’s server can use the corresponding public key, published in the sender's DNS records, to verify the authenticity of the signature.

This capability is crucial for ensuring the integrity and authenticity of the email. It verifies that the message was not altered in transit and that it genuinely comes from the domain it claims to originate from. The use of DKIM helps in defeating email spoofing and ensures that recipients can trust the emails they receive.

In contrast, other options serve different functions. STARTTLS is a protocol used for using encryption in transit but does not provide email verification. SPF, or Sender Policy Framework, helps to prevent sender address forgery by specifying which IP addresses are authorized to send emails on behalf of a domain, but it does not involve signatures. DMARC, or Domain-based Message Authentication, Reporting, and Conformance, builds upon DKIM and SPF to provide a policy framework for email authentication