To email the active document as attachment, click the Send document by email toolbar button, or choose the File | Email | Send by Email... menu command.
To send all open documents as attachments of the same message, choose the File | Email | Send All by Email... menu command.
To zip the documents and attach them to a new email message, ready to be sent in your default mailer, choose the File | Email | Send by Email Zipped... or File | Email | Send All by Email Zipped... menu commands.
To email the contents of a document not as attachment, but as a direct email message: