Fortunately, you can still find the updated document on your hard drive. Here’s where to look.
Where Attachments Opened From Mac OS X Mail Are Stored
When you open an attachment from Mac OS X Mail, a copy is placed in the Mail Downloads folder by default. To find that folder’s common location: Files you have opened in Mail will be in sub-folders. You can arrange them by creation date, for example, to find the most recently opened file fast: ~/Library/Containers/com.apple.mail/Data/Library/Mail Downloads/
Make Mac OS X Mail Store Attachments on the Desktop
If you want to keep track of files opened from Mail more tightly, you can change the folder used to save attachments and downloads, to your desktop, for example.
Click the list view icon at the top of the window.Select As List under the View menu.Press Command+2.
Mail Manages the Files Automatically
Mail will never delete a file you opened, edited, and saved. It will, however, remove any files associated with deleted messages. You can prevent this by changing the setting under Remove unedited downloads: to Never.
