Yahoo! Mail is starting to roll out the result of a massive, retroactive reindexing of user mail and upgrade of Yahoo! Mail's search tools. The upgrade has not reached my account yet (it will take months to propogate through all accounts), but based on the feature list sent me by Karen Mahon at Yahoo!, and Michael Bazeley's review, the improvements seem to raise the bar set by Google. Google's landmark accomplishment was to index the entire contents of the account, not just header fields, and then offer a basic Googling experience. Yahoo! intends to offer the same deep indexing (including the content of attachments) and better search tools:

• Thumbnail views of photos and attachments.

• Preview snippets.

• Search refinement by sender, filetype, messge status, date, or attachment type.

• Album-style views of photos or attachments.

This shot from out of the blue is the first serious challenge to Gmail since Google forced competitors to unsuccessfully chase its ever-expanding storage capacity. Very smart of Yahoo!: Put Google on the defensive where it really hurts, in search. But the truth is that it's painfully difficult to get consumers to switch email providers.