During an investigation of potential spear-phishing, a cybersecurity analyst reviews an email's technical details and notices the following in the message header: 'Authentication-Results: example.com; auth=fail'. What does this most likely indicate about the email?
The email did not meet one or more authentication methods required by the recipient's domain, suggesting potentially fraudulent contents.
The message was sent using a misconfigured Simple Mail Transfer Protocol (SMTP) server, complicating deliverability.
The email contains a reply-to address that does not match the sender address, which is commonly seen in legitimate automated messages.
The content of the message is encrypted, but the public key offered does not match the recipient's private key.