POP3 Mail & Address Book contacts have gone!

Question

I recently did some housekeeping on my Mum's iBook G4 (OSX 10.4.10), part of which was purchasing and installing SpamSieve into Mail. This all went fine. Today she said all the mail in her POP3 inbox had gone, she couldn't send/receive and all her address book contacts had gone (Except hers and Apples).
I've got the iBook now and have noticed that her account type in Mail has somehow changed to a .Mac account (did I somehow do this, or did she???). This is obviously the root of the problem as the
email address now has '@mac.com' appended to the end and the incoming mail server is now 'mail.mac.com' and the outgoing is 'smtp.mac.com:heremailaddress' which is all wrong. I'm unable to change the account type back to POP or the incoming mail server from 'mail.mac.com' (it's greyed out) back to what it was.
I have now created a second account with the correct POP settings and have received in all unread email, but the read email messages have gone. I am unable to send as the new correct pop account is only offered the incorrect outgoing server ('smtp.mac.com:heremailaddress').
Having read several post on this forum, I feel the Mail/Address Book issues are connected and that maybe the application(s) database(s) have been corrupted. I've tried the Address Book remedy at http://discussions.apple.com/thread.jspa?messageID=5248351&#5248351 but this does nothing. The 'user'>Library>Mail folder shows the two accounts as two separate folders. The recently recreated account folder has the new unread messages in the 'INBOX.mbox folder, but the older account folder (which now has 'MAC-' added to the front of its name) only has 'info.plist' in a 'INBOX.imapmbox' folder!
I don't believe any back-ups are available. Can anyone help me restore her old unread mail, and possibly her address book contacts?
I've also just noticed that SpamSieve does not launch as it should when I launch Mail, even though It was purchased and the scripts installed correctly.

Answer 1

Didn’t you make a backup prior to the housekeeping?
I don’t know why would Spotlight find contacts that are gone from Address Book (if that’s what you mean), but as far as Mail goes, under some circumstances (e.g. lack of available disk space, filesystem corruption, repeated crashes), Mail may discard the current ~/Library/Preferences/com.apple.mail.plist preferences file and create a new one. This file is where all the account settings are stored. As a result, all the non-.Mac account settings (but not the messages themselves) are lost. If you had a .Mac account, its settings would appear to have been preserved because Mail would set up that account automatically using the System Preferences > .Mac settings.
What’s the capacity and space available on the 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
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 the filesystem issues, if any, and ensuring 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 ~/Library/Preferences/com.apple.mail.plist from a backup if you have one. Mail shouldn’t be running while you do this.
(2) Set up your mail accounts again (you may want to quit Mail and trash the new com.apple.mail.plist first to start over). 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 trashing the new com.apple.mail.plist and renaming the old com.apple.mail.plist.saved back to com.apple.mail.plist. Again, be sure Mail isn’t running while doing this. Given the circumstances, there exists the possibility that com.apple.mail.plist.saved became corrupt, but that often is not the case and the settings can usually be restored by just renaming the file back to com.apple.mail.plist.
As a side effect of re-creating com.apple.mail.plist, Mail might rename Outbox (which is where messages waiting to be sent are stored) to Delivered. The name of that mailbox is actually a misnomer, as it would contain messages (if any) that couldn’t be delivered for some reason. You can delete that mailbox if you wish.
Note: For those not familiarized with the ~/ notation, it refers to the user’s home folder. That is, ~/Library is the Library folder within the user’s home folder, i.e. /Users/username/Library.