Open the original message details to compare From, Reply-To, and Return-Path. Look for SPF, DKIM, and DMARC results when available, noting that passes do not guarantee trust. Combine indicators with context: Was this expected? Does it match previous behavior? When unsure, escalate or quarantine.
Use a phone number from your contacts, a known calendar invite, or a corporate directory to confirm requests involving money, credentials, or documents. Never reply within the suspect channel. A brief call or chat through verified systems replaces doubt with certainty and breaks the attacker’s momentum.