Which of the following is NOT a requirement for relaxed encryption from Mimecast support?

The correct answer identifies that certificates from unknown authorities are not a requirement for relaxed encryption in Mimecast support. This means that Mimecast does not require certificates to come from authorities that are not recognized or trusted. Instead, relaxed encryption policies typically allow for more lenient criteria concerning key management and standards while still ensuring a baseline of security.

When considering the context of encryption and security protocols, self-signed certificates are indeed a potential option for relaxed encryption scenarios, demonstrating that even without a recognized certificate authority, encryption can still be implemented—though it comes with certain risks. Additionally, a key length of more than 1024 bits falls within acceptable standards for ensuring adequate encryption strength, as it is imperative to maintain robust security measures.

Moreover, certificates without an expiration date would generally be considered poor practice in security because it does not allow for periodic updates and ensures that cryptographic practices can evolve over time. However, in the context of relaxed encryption, such a requirement may not be strictly enforced, but still, standards would suggest that having expiration dates is advisable.

In summary, the option regarding certificates from unknown authorities accurately reflects a lack of requirement from Mimecast for relaxed encryption, emphasizing security adherence while also allowing flexibility in certificate management.