When you open an attached file from Apple's Mac OS X Mail, the appropriate application appears, ready for viewing or even editing. If you edit the file and save it, where are the changes you made? The email still contains the original attachment, and when you reopen it, the unedited document appears.
How to Add Attachments and Files to Emails in Mac OS Mail #TechTips with Jamie Gibbons
Fortunately, you can still find the updated document on your hard drive. Here's where to look.
When you open an attachment from Mac OS X Mail, a copy is placed in the Mail Downloads folder by default. To find the general location of that folder:
In the Finder, select Go to Folder under the Go menu.