Microsoft Migrates 400 Million Outlook Users
May 3, 2013

Microsoft Announces Migration Complete, 400 Million Users

Michael Harper for — Your Universe Online

Microsoft has just announced they´ve finally finished migrating every Hotmail user over to the new service, leaving them with more than 400 million active accounts. In a blog post, Microsoft group program manager Dick Craddock says there were over 150 petabytes of email shuffled from one service to another in a total of six weeks. Craddock also notes 125 million active users are accessing their accounts on a mobile device, thanks to Exchange ActiveSync. To celebrate these achievements, Microsoft is also announcing new features to; SMTP send and deeper integration with SkyDrive, Microsoft´s cloud-based storage offering.

According to the official Outlook blog, there were more than 300 million active Hotmail accounts when came out of preview in February. At this point, there were 60 million active accounts on, presenting Microsoft with quite a challenge in bringing these users together under one service.

“This meant communicating with hundreds of millions of people, upgrading all their mailboxes--equaling more than 150 million gigabytes of data--and making sure that every person's mail, calendar, contacts, folders, and personal preferences were preserved in the upgrade,” writes Craddock in his blog post.

“We've been focused throughout the upgrade on ensuring that every customer has a great experience.”

With the migration complete, Microsoft has also announced two minor tweaks meant to improve´s functionality.

In previous versions of, sending a message from another account, say a Gmail account, would result in a send receipt which included the words “on behalf of,” telling the recipient the email had gone through another account. can now send mail through another account´s SMTP server, getting rid of the “on behalf of” dialogue. This new feature is scheduled to begin rolling out “over the period of a few weeks.”

Microsoft has also added a deeper SkyDrive integration, giving users the ability to insert files and pictures from their SkyDrive into email.

Though Hotmail users have been migrated to, they´re still able to use their old addresses if they choose or register for a new Outlook email address as well. Microsoft also says Hotmail users will not have to make any adjustments to their mobile devices to continue receiving their email.

Craddock and his team may be busy congratulating themselves on a job well done, but some users may still remember the service disruptions during the migration two months ago.

In early March, some Hotmail and Outlook customers were not able to access their email and some SkyDrive customers were unable to access their files. These customers began tweeting about their disruptions, and four hours later Microsoft acknowledged these issues on their Service Status page. Some Hotmail and customers were without email for a total of eight hours, while SkyDrive customers fared better with a three-hour outage.