Digital signatures ensure the integrity and non-repudiation of emails. Integrity ensures that the message has not been altered in transit, as the digital signature would be invalidated if the content were tampered with. Non-repudiation ensures that the sender cannot deny having sent the email, as the digital signature is unique to their identity. These principles are crucial for legal validity, as recommended by CompTIA Security+ standards. Confidentiality (A) and privacy (C) relate to encryption, while authorization (F) and anonymity (D) are unrelated to the primary purpose of digital signatures in this context.