There are some nice new features in the new version of Yahoo Mail.
1. Attachments – preview photos in a slideshow right in your mail or download several attachments at once.

2. Auto-check for new messages – never hit the “refresh” button again!

3. Auto-save drafts – it automatically save emails as you write.

4. Calendar timeline – view, edit, and delete upcoming events on your calendar without leaving your mail.

5. Chat and text from your inbox

6. Drag and drop – drag messages into folders, trash.

7. Toggle back and forth between messages.

8. Peek inside any message with the reading pane

9. Search inside mail – search for and find anything in messages, attachments, names, words, and photos.

10. Universally available so you can stay connected on any internet-enabled phone

11. Unlimited storage

See more here: http://overview.mail.yahoo.com/products/new