Depending on where you are in the world and what profession you are in, Windows Live Messenger is either a professional tool you use every day to keep up with your colleagues or something only teenagers would use. Starting today, Messenger - which Microsoft is already positioning as a social networking client - will become more appealing to professionals, as Microsoft is introducing a deep integration with LinkedIn in the U.S. Thanks to this integration, Messenger users will not just be able to send status updates to LinkedIn and view your colleagues updates, but your Messenger and Hotmail contacts will also be kept in sync across the Windows Live and LinkedIn platforms.

In addition to the Windows Live desktop and web apps, Microsoft's Messenger app for the iPhone will also now offer support for LinkedIn.

Microsoft's Mission: Integrate the Best Products - Don't Reinvent the Wheel

As Dharmesh Mehta, Microsoft's director of product management for Windows Live, told us earlier this week, the company has no interest in building its own social network when tools like Facebook (which is already integrated in Microsoft Messenger and Windows Live) and LinkedIn perfectly good alternatives. Instead, Microsoft is not focused on integrating these services into its own applications. For the most part, these integrations are built on top of open APIs and standards, though the LinkedIn integration also includes some "custom coding," as Mehta described it.

Besides the ability to see LinkedIn updates in your Messenger and post them directly from the application, the most important new feature that this partnership introduces is the unified contacts list that allows you to easily send an email to one of your LinkedIn contacts from Hotmail, for example.

Thanks to this, your LinkedIn contacts are now also available in other Windows Live apps like the Photo Gallery. Due to the nature of LinkedIn, you probably don't want to send a lot of photos to your LinkedIn stream, but, as Microsoft notes, this allows you to easily tag a photo with a contacts name so that you can "put a face to a name."

Of course, you can also use the Windows Live web service to push updates to LinkedIn, though it is probably best to remain vigilant about which updates are appropriate for LinkedIn and which should go to Facebook instead. In addition, you can also syndicate your LinkedIn to your Windows Live feed, so that your friends who are not on LinkedIn can see your updates there.

Bonus: More Hotmail Updates

Earlier today, Microsoft also announced a number of new features for Hotmail. Among these, is the ability to send very large attachments (up to 10GB) by uploading the content to SkyDrive, in-line video support for Dailymotion and Justin.tv, as well as the ability to see the status of your US Postal Service, UPS and DHL packages right in your mailbox (assuming the tracking number is in the email).