We"ve parked your Mail account next to the tractor

http://updates.mail.yahoo.com/blog/archives/11

Ever notice that the URL of your Yahoo! Mail account looks something
like http://us.f348.mail.yahoo.com... when you log in? And did you ever
wonder what that 'f' meant? Or the number next to it?

Well...we know you've been wondering. Because many have asked! So
here it is, straight from the horse's mouth.

Your email is stored on a server, and a collection of servers is called
a "farm" - which is what the "f" stands for. And farms have
numbers. "f348" means your account is on farm 348. Now, f348 is a
great farm! They're all great farms. But we regularly move accounts
from farm to farm to balance the load on our servers. So there's no
guarantee your account will be on any specific farm for any amount of
time.



When we've got a new version of the Beta ready, we release it to just
a few farms at first, and if your account happens to be on one of those
"first" farms at that time, you'll be among the first to enjoy
the new version. If all goes well with the release to those few farms,
we roll it out to the rest.

Cheers,

The Yahoo! Mail Team