I looked at my site and forums and the wiki, but so far I have not been able to find the answer to this question.
Where can I find a list of SendGrid API error codes and messages?
thank
Web UI Link
Link to Web Interface v3
https://sendgrid.com/docs/API_Reference/Web_API_v3/Mail/errors.html
This explains each of the errors or status codes.
if you get 4xx, try using a different key with different permissions. if you get 2xx, you're done. If it is 5xx, then there is a problem / error on the server side.
Happy hack