Mailboxes STILL empty after importing from 10.3.9 to 10.4.11

Question

Hi... I've been spending the last couple of days trawling the web (incl. this site) for solutions and have found similar postings, but they were either unresolved, or didn't really match my situation. So please excuse me if this is partially repetitive but hopefully someone can point me in a specific direction for resolution.
1) Under Mail 1.3.11 (Panther 10.3.9) I had stored several years of email (8+ GB... unfortunately my work requires me to keep everything) from 3 accounts - 1x IMAP, 2x POP. Most of my mail had been reorganised into various folders and mailboxes that contained a mixture of emails from all 3 source accounts. As far as I know, everything was healthy - no corruptions etc. except for the ubiquitous "not downloaded from server, take account online" problem.
2) When I transitioned to Mail 2.1.3 (Tiger 10.4.11) I used the Migration Assistant and got all my old Mail data over, changed all the file and folder permissions in olduser-Library-Mail to read and write, and used Import within Tiger Mail (and using the Other option as well). Everything seemed to move over into an Imported folder, and my hierarchy of subfolders remained correct, but all of them are empty.
3) Some suggestions I've found online have been to Rebuild the "empty" mailboxes/subfolders but the Rebuild option is grayed out whenever I select any mailbox/folder/subfolder.
4) There were some other suggestions to tinker with the insides of newuser-Library-Mail or olduser-Library-Mail but these were not for situations identical to mine so I'm hesitant to try for fear of making things worse.
5) For the moment, to continue working, I've set up a new account under Mail to fetch and send from my main IMAP account, but I don't have any of my old emails for reference ie. my new Tiger Mail has one mailbox (the Inbox) containing all my incoming mail from AFTER the upgrade... everything prior to that is on an external firewire drive that I can boot into (the old 10.3.9) as a reference backup. Curiously, eventhough I've set the new Tiger Mail to keep copies of outgoing mail, my Sent box remains empty and sometimes when I'm composing outgoing mail, I get a warning pop up about being unable to save into my IMAP outbox.
Do all of the above give any gurus out there a lightbulb moment as to what my problem might be and how I can solve it? Any help will be rewarded with eternal gratitude and my first grandchild. OK, maybe not the latter, but please help anyway!

Answer 1

No, Mail in 10.4 is not crap; it's actually better and more reliable than Mail in 10.5. So here's what I would do, though this will not preserve any folder hierarchy--you'd have to manually do that:
1. In your Panther Mail program, choose an account, a mailbox (Inbox for this example), and Select All messages in that mailbox.
2. Choose Save As… and choose Raw Message Source from the dialog window, then choose a destination (your Desktop) and save the file as Inbox.mbox.
3. After that file is saved, go to your Desktop and create two new folders: one named Inbox and the other named Mailbox.
4. Put the Inbox.mbox file inside the Mailbox folder, and the Mailbox folder inside the Inbox folder. Copy the nested folder/file to the Tiger machine if necessary so you can access it from Tiger Mail.
5. Open Tiger Mail, choose File >Import Mailboxes…, select Other from the list of import options, then navigate to the Inbox folder and select Choose. The file Inbox.mbox should appear in the window; click Continue and wait for the import to finish. You can then move the Inbox messages out of the Import folder to wherever you like in Tiger Mail.
6. Rinse and repeat for your other mailboxes, changing the names of nested folders/files as necessary.
Mulder