Like many people, Max Shafiq is looking 
on the Apple Discussion forums for a way to import Tiger Mail messages into Leopard Mail.
Another post in the same thread notes some of the ways not to do it:
I have the same problem Max. I’ve tried importing mailboxes (from the file menu), and also dragging the old Mail folders to the new Mac’s Library… both attempts only partially successful, with most mail missing completely.
Actually, the answer is fairly simple. Just follow the method in this previous Hawk Wings’ post on importing emlx messages into Tiger Mail. Nothing’s changed.
It involves quitting Mail, making a backup, creating a new Mailbox in your ~/Library/Mail/Mailboxes folder, copying in the individual emlx files (that is, the messages) you want to import, restarting Mail, selecting the new mailbox which will appear in the list of mailboxes “On my Mac” and rebuilding it. Voilà ! The messages appear, with timestamps and everything else nicely preserved.
Piece of cake.
Mailboxer is a smart little utility that quickly creates a smart mailbox in Mail.app for each of the contacts in your Address Book.
Now I have a manageable number of smart mailboxes that I will use at least ten or fifteen times a day. That’s a lot of typing into Mail’s search field that I have saved myself.
Chris Landon emails with a reasonable request, something you don’t miss or even think about until someone else mentions it. 
Greg Welch, creator of 
Microsoft is recommending that that employers increase the size of Exchange mailboxes, as it moves to head off the increasing trend among workers to auto-forward their email to more expansive Gmail accounts.
Daniel Bingham has written a plugin that fixes a particular problem with Mail.app’s IMAP support. 
