I'm interested in how this works at a technical level - is it implemented as plugins for Exchange and other servers, or is it some kind of proxy that clients connect to instead of directly to their email server?
I'm still bound by various paperwork that (probably) prevents me from disclosing that, but if you root around on the company site you can find a few relevant patents with details.
It's probably straight-forward to do. Parse image links from the email, send those links to imgur, and replace the original image links with the imgur ones.
That's about 1% of the work. Email is old, arcane at times, and has a ton of interoperability and vendor-specific nonsense. Add in the fact that it _cannot_ go down for enterprise and that you have to do all of this at huge scale and it turns in to a pretty tough problem to solve.
I also used to work at message control. The architecture to support all of the legacy and new technology for email was very hard. Also architecting a system to ensure that it would never go down completely was a large challenge.
You also have to understand how providers deal with email to make sure delivery is never affected. We had to ensure 100% delivery and never fail.
