So long, Hotmail. It was nice to know you.

Microsoft unveiled a major update to its consumer mail platform today, with a new look, a slew of new features, and a new name that is surprisingly familiar.

The “modern email” service has been in super stealth mode for several months under the codename NewMail. With its formal launch as an open-to-the-public preview, the service gets a new name: Outlook.com. I’ve been using the NewMail beta for a week now and can share some first impressions here.

Outlook, of course, is the serious, business-focused mail client included with Office. Microsoft used the brand with Outlook Express, its lightweight email client in Windows XP, but dumped the name with the launch of Windows Vista in 2006.

Restoring the Outlook name to Microsoft’s consumer email service accomplishes two goals. First, it dumps the Hotmail brand, which is tarnished beyond redemption, especially among technically sophisticated users who have embraced Google’s Gmail as the default standard for webmail. More importantly, it replaces the Hotmail domain with a fresh top-level domain that’s serious enough for business use.

(If you have an existing Hotmail.com or Live.com address, you can continue to use it with the new Outlook interface. But new addresses in the Outlook.com domain are up for grabs. if you have a common name, I recommend that you get yourself over to Outlook.com now to claim your preferred email address while it’s still available.)

The Outlook.com preview will run alongside Hotmail for now, but when the preview ends, this will be the replacement for all Hotmail and Live Mail users.

With Outlook.com, Microsoft is taking dead aim at Gmail, positioning Google’s flagship service as the old and tired player that is ready for retirement. Gmail, they point out, is eight years old, and its interface and feature set aren’t exactly modern. It doesn’t play well with any social media except its own, it handles attachments in a stodgy and traditional way, and it’s not particularly elegant when it comes to managing the deluge of email we all have to deal with every day.

So what’s new about NewMail—sorry, Outlook.com? And why would anyone consider switching from Gmail?

The most obvious change in the web interface, of course, is the overall design, which gets the full Metro treatment.

That three-pane layout follows the familiar Outlook standard, but the typography is definitely new. It’s clean and crisp with no wasted ornamentation or clutter. It should come as no surprise that the default organization is optimized for use on touch-enabled devices.

A pane on the right shows different content, depending on the context. If you're communicating with a friend of colleague who's in your address book or connected via a social-media service, you'll see updates about that person on the right side, with the option to chat with them (via Messenger or Facebook chat) in that pane. In a demo, Microsoft showed off Skype integration and said it will be coming later in the preview.

If you've selected no message, the right pane might show ads, which appear in Metro style boxes with text--an image preview appears if you hover over the ad. As part of its positioning against Google, Microsoft has taken pains to note that your messages aren't scanned to provide context-sensitive ads, as they are with Gmail.

This is a pure HTML interface, which means the functionality is consistent across different browsers and on alternative platforms. I tested NewMail on a Mac using Safari and Chrome and in both Firefox and Chrome on several Windows PCs. Everything worked as expected. I also tested the web-based interface in mobile Safari on an iPad, where it also displayed perfectly (after switching from the default mobile layout).

On mobile devices, you’ll be able to use native apps. An app for iOS devices should be available immediately. Microsoft promises an Android app “soon” that will enable Exchange ActiveSync support for older Android versions.

A few pieces of the web-based UI are worth calling out separately. You'll find screenshots and details on the next page.

A command bar at the top of the page provides access to commands as needed. If a command isn’t available in the current context, it’s not visible on the screen.

The preview pane (a feature that’s still experimental in Gmail even after eight years) lets you read and reply to messages without leaving the main screen. Action icons that appear when you move the mouse over an item in the message list let you file, delete, or flag the message with a single click or tap.

The new Outlook has some impressive mail management smarts built in. It automatically recognizes newsletters and other recurring types of mail. A Schedule cleanup option in the message header (also available on the command bar), lets you create rules on the fly that automatically delete or file similar messages to reduce clutter. You can specify, for example, that you want to keep only the most recent message from a “daily deals” site. You can also define how many messages you want to keep from a particular sender or automatically delete/file newsletters after a set number of days.

For newsletters that don’t contain an obvious unsubscribe link, the new Outlook adds a universal unsubscribe feature at the bottom of the message. When you select this option the web service sends an unsubscribe request on your behalf and creates a message-blocking rule.

One huge differentiator between old-school webmail services like Gmail is the new Unified Address Book in Outlook.com. It takes a page from Microsoft’s People hubs in Windows 8 and the Windows Phone platform to pull together your traditional address book—where you manage names and details—and combine it with social media services of which you’re a member.

The advantage, of course, is that you always have the most up-to-date contact information for friends and colleagues, assuming they update their profiles. The new Outlook does a pretty good job of combining records. If you have contacts that appear in multiple locations, you can manually link or unlink those records as needed.

Supported services include anything you can link to your Microsoft account, including Facebook, Twitter, LinkedIn, and Flickr. You can import contacts from Google and Facebook if you want to keep them locally.

In terms of creating and sending photos and file attachments, the new Outlook integrates exceptionally well with SkyDrive, so that you can email large attachments and photo albums, storing them on SkyDrive with well-integrated links that the recipient can access with a click. The spec sheet says single attachments can be up to 300 MB in size. If they're stored on SkyDrive, you don't have to worry about the message being rejected by the recipient's mail service.

And of course, the service incorporates all of the Office Web Apps, which makes the process of sharing Word documents, PowerPoint slide decks, and Excel workbooks much more seamless.

On the back end, the interface for managing an email account is cleaner. You can still create aliases that you use for sites and contacts where you don’t want to share your real address. And if you just want to experiment with the new service, you can redirect your Gmail messages temporarily to the new account or sign in with an existing Hotmail or Live address. (I’ve had my Gmail account redirected to Hotmail for a year without problems.)

I’ve put together a screenshot gallery showing off some of the new features. (See "A guided tour of the new Outlook.com." ) I’ll also be putting together a FAQ to help sort out your options for linking and forwarding existing email accounts.