Outlook.com hits 400 million accounts as Microsoft officially kills off Hotmail

Four hundred million. Four. Hundred. Million. That’s how many active email accounts Microsoft has amassed over on Outlook.com. Really.

According to Outlook.com’s group program manager Dick Craddock, the company hit the milestone yesterday after it finished moving over all existing Hotmail accounts to its brand new web-based email service. Before you start wondering how on earth Microsoft managed to get all those millions to sign up less than four months after the launch, consider the fact that there were already around 300-million active Hotmail accounts which have now been transferred to Outlook. That means that around 100-million new accounts were actually created on Outlook.com itself.

The service did witness stellar growth organically, hitting 1-million new sign ups just hours after its launch in January and 10-million two weeks later. To put the number in perspective, 400-million is equal to the number of total Google+ sign ups in September last year, and double Twitter’s last reported monthly active user figures. But Microsoft still has a way to go before it reaches Gmail-level adoption: the world’s most popular web-based email provider said that it had 425-million active users in June 2012.

Now that Hotmail is officially dead, Outlook is focusing on adding new features, like including deep integration of Microsoft’s cloud storage service, SkyDrive, into its email client. It’s rolling out a new option to include shared images and files from your SkyDrive in emails, instead of uploading them as attachments.

Craddock also explained how the process of porting all those Hotmail accounts over to Outlook involved shifting over 150 petabytes (million gigabytes) of email in 6 weeks. Microsoft has released an infographic to explain just how much data was transferred in that time period, comparing the volume of files to everything from the height of Mount Everest to the time it would take to listen to 150-million gigabytes of music.