Hi @salutethepig,
It looks like your second image contains broken link as a fallback option. The Optimole URL specifies some parameters of the image, as well as the fallback URL.
In the first URL, it’s https://chrisbulow.uk/wp-content/uploads/2024/10/1440px-Detroit_Edison_Power_Substation_Church_Street_Lake_Orion_MI_-_53011839702.webp – which will load the image.
But in the second URL, it’s https://chrisbulow.uk/Waether-station.webp, which links to a Not Found page instead of an image.
The way services like Optimole work is that they have servers around the globe, so they can deliver the image as fast as possible. In your case, my guess would be, that the image is cached in some of the servers, but not all. And those that don’t have it will try to load it from the URL you provided – https://chrisbulow.uk/Waether-station.webp, which results in a broken image.
Changing the last part of second URL to correctly link to the image you need should fix the issue.
Thanks; I didn’t think this was looking like a MailPoet issue but as I’m told that the Optimole process is automatic, (I simply pick the images from the Media Library which should have the correct links to Optimole and add them to the post) I’ll ask them for assistance there.