What a week it's been for Yahoo! Mail. Tuesday they leap fogged Google by announcing virtually unlimited storage for all of their Yahoo! Mail users. Today they've introduced an API which exposes the world's most popular web mail platform and opens it up for enhancement to legends of web developers, mashup hackers, and API vultures.

The Yahoo! Mail Web Service, as they are calling it, is a complete set of SOAP services that developers can use to access Yahoo! Mail accounts. The services are divided into two tiers. The first is for all Yahoo! Mail users and provides methods for listing folders, listing messages, moving messages, and the like. The second tier is limited to premium (Yahoo! Mail Plus) accounts and gives full access to message text, attachments, the message search feature, and more.

A new frontier for mail.

"This is a very exciting release for us. Our goal is to open up Yahoo! Mail and its expansive user base to a whole new frontier of possible tools, hacks, and community driven mashups. Most of which we can't even envision yet. " - John Kremer , VP Yahoo! Mail.

Video, Hack Ideas, and more after the jump.

By breaking it into two tiers Yahoo! is adding value to their Plus users while letting developers, in essence, create whole new clients to read and interact with the Yahoo! Mail platform. One obvious example would be to create a client for mobile devices. Another might be a specialized MiiMail for Nintendo Wii users who want to access their Yahoo! Mail accounts in a more TV friendly environment. They are even incentivising developers to use the Premium API methods by offering them a commission on any new Plus memberships that are generated as a result of their app.

A massive user base that is hungry for new functionality.

"The Yahoo! Mail Web Service is a huge new addition to our development community! Rather than building a mail platform from scratch developers can integrate their software with our platform and take advantage of our massive user base and extensive infrastructure." - Chad Dickerson, Head of Yahoo! Developer Network

It is easy to imagine developers using these services to build a plethora of tools and mashups. In this Screencast example Leah Culver shows how she used the Mail APIs and a Greesemonkey script to add a Send Postcard button to Flickr images. This is pretty cool and well worth a look.



Cool, huh? Here are a couple of my own ideas, feel free to run with them:

1. YFilters - How about creating an inbox organizationally utility that would let you organize messages in a much more customizeable way than you can using Yahoo!'s own filters? Imagine logging into a YFilters tool and creating custom set of filters to move messages around based on contact name, subject line, replied status, date, attachments, or combinations of the above. You could have a regular GTD tool on your hands in no time.
2. YToDoList - Why not add Yahoo! Mail support to a To Do list application? If you are dependent on someone else to get something done, just click the mail icon and write them an email. Then, when they reply, display the message in a dialog along side the item in your list.
   

What is next...

As a big Yahoo! Mail fan boy I can tell you that this is very exciting. It is a little disappointing that they didn't open up all the APIs for free mail accounts. But if, they become popular enough with users, who knows? Chad Dickerson promises that this is only the beginning of what we'll see from Yahoo! and it is certainly a bold move in the right direction.

If you want a more detailed technical overview check out this screencast and be sure and read the documentation. They also have some free code samples for you to use. No word yet on when and how you can use this with Yahoo! Pipes, but no doubt someone out there will come up with a hack before long. Yahoo! has also put together a gallery for people to share their creations.