Microsoft today announced it has completed moving its users over to, roughly nine months after first taking the wraps off its revamped email service at the end of July 2012. According to the company, there are currently 400 million active accounts, noting that the growing organic excitement over the service helped pushed that number up from "over 300 million" at Hotmail's peak.

That's also up from 60 million active accounts when came out of preview in February, and out of the total number of users, there are 125 million that are accessing email, calendar and contacts on a mobile device via Exchange ActiveSync. All in all, 150 petabyes of email data were migrated over the past six weeks.

To celebrate the milestone Microsoft is also rolling out two significant upgrades to the service: SMTP Send and deeper SkyDrive integration. The former streamlines the process of sending email from an alias, including non-Outlook addresses, without recipients seeing a message saying "Sent on behalf of...".

As for the improved SkyDrive integration, it specifically centers on the message composer, which now allows users to select SkyDrive photos and files from the cloud storage service and automatically turn those into the right thumbnails with links that have the right permissions tied to people that receive the email.

Both new features are rolling out today. Microsoft says SMTP should be available immediately to all users worldwide, while the SkyDrive integration is being rolled out gradually over the next few weeks.