Configuring a new mail account in Office 365 beta’s Outlook Web App can be done using the Outlook Options link available as part of the Home Screen.
By clicking the Options link, the following Mail Option screen will be displayed. To add a new account you can either click on the Connected Accounts link or select the shortcut option See e-mail from all your accounts in one place.
Under Connected Accounts, click the New link option.
This would display the screen for entering the New Account Connection. Provide the required fields, email address and password and then click the Next button.
This would display the following progress message.
If your account has been successfully configured then you would get a confirmation message as shown below. Click the Finish link to complete the New Mail Account Configuration in Office 365.
By this way you can use the Outlook Web App available as part of the Office 365 to configure different email accounts such as Gmail, Yahoo Hotmail and other service providers account. And check emails from all these account under one place i.e your Outlook Web App.