Whenever you send an email, a copy is stored in your sent items (unless you have it disabled) which keeps a syncronous history of your activity. This functionality can be useful for doing simple version control.

If you are not familiar with version control, in a nutshell it means different versions of a file are snapshotted at various points so you can roll back to a previous version or review changes. Of course email is not designed to do this, but it can work pretty well.

Just email a file to yourself at various points and you now have a snapshot version you can rollback to or review. Additionally, you can include notes in the body of the message which you can later search on.