Apparently, all major search engines promote Yahoo! Mail at top of search results page for query "Email". So, if you have never used the email before (very unlikely unless you were in hibernation for last 15 years), are looking for an email service and search for it in all major search engines; it would list Yahoo! Mail at the top.

Here are screenshots:

Interesting to note here that Live search doesn't even list "GMail" in "Related searches" and in search results of first page.

Look carefully at the sponsored links in Yahoo! below. Google must be paying boatloads of money to Yahoo! to make sure they appear on top.

Is it a mere coincident or that they all think that the term "Email" is the most relevant to "Yahoo Mail"?