Use a proxy only if you still need one. For rate limits on Bing Images, enable Interval first.

Open Magic Post Thumbnail > Automatic > Pre-Processing & Developer and set Interval (for example 1 or 2 images per minute). That spaces generations without a proxy.

The proxy option (Pro) can still help if Bing or another photo source blocks your server IP. Configure it under Magic Post Thumbnail > Proxy. You must use a proxy with the HTTPS protocol.

Check with your host: some firewalls block outbound requests through proxies.