Today, we have reason to celebrate, as we’ve begun to roll out the new Hotmail worldwide!
You may start seeing the new features
in you inbox as early as today, features like the new Sweep menu, the freshly integrated Office Web Apps, huge new attachment limits up to 10 GB using SkyDrive, and the ability to create and send photo albums right from Hotmail. If you don’t see these features today, please hold on just a little while longer – everybody will be upgraded this summer.
You might be wondering why everybody doesn’t get the new version immediately. Well, as my friend Phil explained in his blog post Hotmail tips the scales
, our Hotmail servers are grouped into clusters, and we have hundreds of clusters. We start by upgrading a single cluster, wait to make sure that it’s running smoothly and that we didn’t miss anything during testing, and then we continue on to the next cluster. If we find a bug, we’ll fix it before continuing further, and give that fix to everybody who has been upgraded so far. That way, we release the highest quality code as we proceed, and we can minimize downtime for everybody. Accounts are assigned to clusters to best balance our total account load, not by country or by tenure of the account, so each account is as likely as the next to be upgraded. Given this, we can’t move any individual accounts up or down the migration line.
Additionally, while most people will see all the new features at once, as soon as their cluster is upgraded, some features, like the integrated Office Web Apps
and the ability to send files via SkyDrive, will initially be available only in certain countries.  For example, Office integration will first roll out to Hotmail customers in the US, Canada, UK, and Ireland first, and then to customers in other countries later this year.
We're as eager as you are for everybody to have access to the new Hotmail
, and we hope that you’ll love it as much as we do, too.
- Mike Schackwitz
Program Manager, Windows Live Hotmail team