You are also required to whitelist https://api.smartup.io which is our backend load balancer's dns name.
We use Amazon CloudFront as our CDN so you may also need to whitelist *.cloudfront.net.
Our Certification Authorities Root certificates can be found on the following link: https://www.amazontrust.com/repository/.
Our service is HTTPS only (standard port 443), but opening port 80 may be necessary if you'd like your users to be redirected if they access our domain using explicit "http" URL schema. (Some browsers tend to do that).
On our API we serve information exclusively on HTTPS (443). Establishing connection without encryption is not possible.