No suitable replacemsg command found for "Following phishing URLs are detected by Fortigate" message

Looks hardcoded so if you want to modify this message, maybe you should play with FortiAnalyzer and Automation Stitches...

Hello 

that phishing URLs are being detected by FortiGate, suggests that the email you're sending contains a link that has been flagged as potentially malicious or associated with phishing activity. FortiGate's security features, including the Anti-Spam module, might be blocking the email due to the presence of such URLs.

Visit the FortiGuard URL link provided in your solution (https://www.fortiguard.com/faq/antispam/blocklist). This contains information about how to check the reputation of the URL or domain in question. FortiGuard provides real-time updates on malicious URLs and domains, and checking here can help you determine if the URL you're sending is flagged for a legitimate reason.

Thanks