Yahoo has started including Read and Read+Write access to full message contents for Yahoo Mail users with the Yahoo Mail API.
“We’ve added these expanded scopes — we’ve been allowing message-header access for years — so that the hundreds of millions of users who entrust their data to us can have the freedom to use it in whichever context is most useful to them,” says Yahoo.
“The API has also been ported to OAuth, providing a much cleaner token model, better authentication UI, and more fine-grained management for developers,” the company adds. “We’ll continue to support Browser-Based Auth for legacy developers, but its use is deprecated. We recommend that anyone starting a new project choose OAuth.”
Documentation can be found here. There is a discussion forum for conversation about the API, and this Twitter account will post updates.