Email signatures provide non-repudiation, which ensures that the sender of an email cannot deny having sent it. A digital signature, when attached to an email, uses cryptographic techniques toverify the sender's identity and confirm the authenticity of the message. This feature helps establish trust by preventing tampering and ensuring the integrity of the communication. CASP+ emphasizes the role of digital signatures in ensuring non- repudiation in secure communication protocols. References: CASP+ CAS-004 Exam Objectives: Domain 2.0 - Enterprise Security Operations (Non-repudiation and Digital Signatures) CompTIA CASP+ Study Guide: Email Security and Non-repudiation with Digital Signatures