Sign in with the account you use for SkyDrive, Xbox LIVE, Outlook.com, or other Microsoft services.
Sign in with the account provided by your work or school to use with Office 365 or other Microsoft services.
When you have a collection of email messages that you want to forward, you don't have to forward each one individually.
You can attach multiple messages as attachments to a single message. It's a fast way to send someone a set of messages.