Resource not found after deployment for endpoint

Question

I am using next.js.

endpoint works well locally.
After deployment, the endpoint located in api/mail cannot be found, and Post request failed

try {
            const response = await fetch(
              "/api/mail",
              {
                method: "POST",
                headers: {
                    'Content-Type': 'application/json',
                  },
                body: JSON.stringify(data)
              }
            );