This detection rule identifies attempts to impersonate SendGrid in inbound messages. It utilizes various string manipulation techniques, such as Levenshtein distance and case-insensitive matching, to analyze the sender's display name and email address for any signs of brand impersonation. Specifically, the rule looks for names or parts of email addresses that closely resemble 'SendGrid' and checks if these messages contain security or authentication-related themes with a high confidence level, indicating potential malicious intent. Additionally, it ensures that the sender is not from recognized organizational domains or legitimate SendGrid domains while failing authentication checks. The rule further incorporates checks against high trust sender domains to filter out false positives from trusted sources. By analyzing message content, headers, and sender profiles, the rule aims to mitigate risks associated with Business Email Compromise (BEC), phishing attempts, and spam originating from untrusted sources.