Public/Private keypair. A public/private keypair is a pair of cryptographic keys that are used to generate and verify digital signatures. The private key is used to sign the email message, while the public key is used to verify the signature. The public key is published in a DNS record, while the private key is stored on the Cisco Secure Email Gateway appliance[1, p. 2].

Domain signing profile. A domain signing profile is a configuration that specifies the domain and selector to use for signing outgoing messages, as well as the signing algorithm, canonicalization method, and header fields to include in the signature. You can create multiple domain signing profiles for different domains or subdomains[1, p. 3].

The other options are not valid because:

A. DMARC verification profile is not a component for utilizing a digital signature in outgoing emails. It is a component for verifying the authenticity of incoming emails based on SPF and DKIM results[2, p. 1].

B. SPF record is not a component for utilizing a digital signature in outgoing emails. It is a component for validating the sender IP address of incoming emails based on a list of authorized IP addresses published in a DNS record[3, p. 1].

E. PKI certificate is not a component for utilizing a digital signature in outgoing emails. It is a component for encrypting and decrypting email messages based on a certificate authority that issues and validates certificates[4, p. 1].