Microsoft has announced that using the Outlook Web App (as well as its mobile versions for the IPad, IPhone and Android) you can now stop sending attachments and instead have these attachments stored in your OneDrive. When you attach a file now from your local computer, you will be asked whether to upload it to OneDrive instead of attaching it:
When you link to a OneDrive file instead of attaching it, you gain permissions for your files that you can use to restrict whether the recipient can edit or just read the file.
In addition, if you are using OneDrive for Business you get the ability access to real time co-authoring using Office Online. There is now a side by side view so you can edit the document in real time and exchange messages with your co-authors.