Lost a few years worth of Mail

Question

Hi all. If anyone can give me any advice I would be most grateful. Just 2 days ago I found that I lost some 3 years worth of mail from my inbox. I have been searching the mail posts and have a few ideas of what to do but no solid answers on how to retrieve my lost messages. Help please. Thanks.
Todd
The following is from my inbox.mbox (package contents):
mbox.SKindex
mbox.SKindex.isValid
tableofcontents
content_index
Info.plist
mbox
iMac 800 MHz PowerPC G4   Mac OS X (10.3.9)   768 MB SDRAM

Answer 1

my POP email account is totally GONE. I logged on a few
days ago and received a welcome message "You have no
email accounts configured to use Mail."
What’s the capacity and space available on your startup disk? Take a look at the comments about disk space in the following article, in case they apply to you:
Problems from insufficient RAM and free hard disk space
Even if there is enough space available on the startup disk, for some reason that remains a mystery to me, Mail sometimes “thinks” it must discard the current ~/Library/Preferences/com.apple.mail.plist preferences file and create a new one. As a result, all your non-Mac account settings (but not the messages themselves), which are stored in that file, are lost.
Verify/repair the startup disk (not just permissions), as described here:
The Repair functions of Disk Utility: what’s it all about?
After having fixed all filesystem issues, if any, and making sure that there’s enough space available on the startup disk (a few GB, plus the space needed to make a backup copy of the Mail folder), quit Mail if it’s running, and make a backup copy of the ~/Library/Mail folder, e.g. by dragging it to the Desktop while holding the Option (Alt) key down, just in case something else goes wrong while trying to solve the problem. This is where all your mail is stored.
You have three options now:
(1) Restore com.apple.mail.plist from a backup if you have one. Mail shouldn’t be running while you do this.
(2) Set up your non-Mac accounts in Mail again. If given the option to import existing mailboxes or something like that, don’t. Just enter the account information and Mail will automagically rediscover the data in ~/Library/Mail/ when done. You’ll also have to re-configure most of your settings in Mail > Preferences. For spam-related security reasons, the first thing you should do is go to Preferences > Viewing and disable Display remote images in HTML messages if it’s enabled.
(3) Mail may have renamed the old preferences file to com.apple.mail.plist.saved. If that’s the case, you may try moving the new com.apple.mail.plist out of ~/Library/Preferences/ (e.g. to the Desktop) and rename the old com.apple.mail.plist.saved back to com.apple.mail.plist. Again, be sure Mail isn’t running while doing this. Since Mail decided to discard it, I would expect this file to be corrupt (I don’t understand why would Mail discard it and create a new one otherwise), but apparently that often is not the case and the settings can indeed be restored by just renaming the file.
Note: For those not familiarized with the ~/ notation, it refers to the user’s home folder, i.e. ~/Library is the Library folder within the user’s home folder.