Starting this week, we're beginning the transition to cloud-based images. Rather than hosting all your images in our London-based data centre, we're going to employ Amazon's cloud infrastructure (AWS) to host your images (and documents). We're doing this to see improved availability and durability, but also for increased download speeds (your images will be loaded from the nearest AWS data centre to your recipient).
Accounts are being migrated over a period of three weeks, and you won't notice anything or have to do anything. You can read more about this — including why we're doing it and the benefits — over at http://www.dotmailer.co.uk/blog/super-resilient-images-served-from-around-the-world/.