I followed the steps from the API documentation and wrote a backend in JavaScript to send emails. Normal emails are sent without any problems. However, I can’t send emails with attachments.

As the documentation says, I first try to upload the file, but I get the following output:

1. {"errorCode":"UPLOAD_RULE_NOT_CONFIGURED","status":{"code":404,"description":"Invalid Input"}}

1. const formData = new FormData();
2. formData.append("file", opts.file, opts.file.name || "attachment");
3. 
   
4. const uploadRes = await fetch(`${baseUrl}/messages/attachments?uploadType=multipart`, {
5. method: "POST",
6. headers: {
7.   Authorization: `Zoho-oauthtoken ${accessToken}`,
8. },
9. body: formData,
10. });