While the Outlook app for Android and iOS have had Google Drive integration for some time, the new integration to the webmail will work the same way as OneNote integration does on Outlook.com.
And the first time you use the Google Drive integration you’ll have to sign-in and authorize Outlook, after clicking on the “attachment” icon and then choose the service to use, you see a pop-up window showing your files.
Microsoft will also be adding a new “attachments view” for message threads, so when a user views a long message thread there will be an attachment icon at the top with the number of attachments that have been included in the thread.
The company also announced Dropbox and Box integration for Outlook.com earlier in the year.
Albeit, these functionalities that integrate other web services to Outlook.com is great for users, Microsoft's aim is to migrate all users to the refresh new interface of Outlook.com.