1. While composing an email message, click the attachment button at the bottom of the message window.
2. By default, your OneDrive folder should be automatically selected. You will be able to browse and select files to attach from your OneDrive library with ease.
3. If you need to upload an attachment from your local computer, click on Computer to bring up the file explorer. Browse for your file and click Open.
4. You will be asked whether you would like Upload and attach as a OneDrive file, or just Attach as a copy. Click on Upload and attach as a OneDrive file to attach the selected document, as well as upload the file to your OneDrive library.
5. Once you send the email with the attachment, you will find your attachment uploaded to a folder called Email attachments in your OneDrive library.