The email system administrator for an organization configured DKIM signing for all email legitimately sent by the organization. Which of the following would most likely indicate an email is malicious

DMARC (Domain-based Message Authentication, Reporting & Conformance) leverages SPF and DKIM to provide a policy framework for email authentication. If a malicious email attempts to spoof the company's domain, and legitimate emails are DKIM signed, the spoofed email will almost certainly fail the DKIM alignment check, leading to a DMARC failure. A DMARC failure with a robust policy (e.g., quarantine or reject) is a strong indicator of a malicious, unauthorized email.

The sending IP address being a hosting provider is not inherently malicious, as many legitimate organizations utilize hosting services for email infrastructure; SPF, DKIM, and DMARC are designed to authenticate such senders.

The phrase 'the signature does not meet corporate standards' is vague and doesn't represent a specific, verifiable email authentication failure like a DMARC check.

Having different sender and reply-to addresses is common and legitimate for various automated or notification emails, so it is not a strong indicator of malicious intent.