When you delete a file, it goes to the recycle bin. Your recycle bin does have a default maximum amount of space it will take up. When more files are deleted, the oldest deleted files are purged. You can find out what that limit is by right mouse clicking on the Recycle Bin icon on the desktop, then selecting "Properties". Of course, if you double-click on the icon it will open up the folder where all the deleted files are, so you can either restore them or permanently delete them.

As for e-mail, if you're using Outlook, I think it maintains it's own "deleted files" archive, and that's managed via Outlook, not through the Recycle Bin.

^ You're welcome, glad to be of help. Remember that when you delete a bunch of e-mail items in Outlook, you may want to look into the options where you can "compact" the deleted files archive. I don't know which version you are using, or if it's Outlook at all. But when I used to use it, I remember being able to shrink archive files after purging items from them, to reclaim disk space.