Does Optimole optimize the third-party images?

Yes, the images from third-party domains can also be optimized and served by Optimole. You need to follow the below steps:

1. The domain where images are stored should be whitelisted under Optimole's Dashboard -> Allowed Domains. 
2. Go to your Optimole WordPress plugin in your WordPress admin -> Media -> Optimole and click Refresh Stats
3. Clear any caching plugin that you use, for more details on this, you can check this document.

After this is done, give it some time and Optimole should start serving your images.