UPDATE: Microsoft no longer supports account linking, so this tip is no longer valid. Please read Microsoft Drops Outlook.com Linked Accounts Feature for more information.
Like many of you, I have multiple Microsoft accounts, or what we used to think of as Windows Live IDs, or more generically, as Hotmail and Outlook.com accounts. And while Microsoft offers no way to merge these accounts, it does at least offer one useful convenience: You can link multiple Microsoft accounts together in Outlook.com, so you don’t need to keep signing in and out to access the information in the different accounts.
To be clear, this capability is limited to the web interface. And it doesn’t answer what is increasingly the number one need of those who rushed to acquire favorite Outlook.com addresses as soon as possible: It doesn’t provide a way to merge an old Hotmail account into a new Outlook.com account. Maybe someday.
In the meantime, linking Microsoft accounts—like a Hotmail account and a new Outlook.com account—does make sense, since it’s otherwise quite ponderous to switch between these accounts on the web. This is especially true if you’re signing in to one of these accounts with, or using one of them for other online services, such as Messenger.
Here’s how to set it up.
From your web browser, navigate to the Microsoft Account management portal and sign in to one of the accounts you'd link to link. (It doesn't matter which one.)
Then, navigate to Permissions.
Under “Switch between Microsoft accounts quickly on the web,” click the link, Manage linked accounts.
Then, click Add linked account. (OK, you could have navigated here directly using this link, but I think it’s a good idea to understand the Microsoft Account management portal and what’s available there.)
From here, enter the password for your currently signed-in Microsoft account and then the user name and password for the account you’d like to link. Then, click Link. Microsoft will link the accounts and then show a list of the accounts you have linked to this accont.
To see how linked accounts work, click the account name/picture in the upper right of the web browser window. (You can do this from here, in Microsoft Account management portal, or from many of the Microsoft online web properties, including Outlook.com Mail, People, and Calendar, SkyDrive, and so on.) As you can see, you can have multiple accounts linked together and switching between them is as easy as selecting the account from the menu.
Obviously, this is especially useful for Outlook.com Mail. But it works in many places.
And linking is a two-way street. There’s no sense of “master” account and “secondary” accounts; you just sign in to whatever account you prefer and the other(s) will be available from that menu.
You can of course unlink accounts too: You do this from the same screen in the Microsoft Account management portal. Here’s a quick link to find it, and then just click the Unlink link to sever the connection.