[Macpartners] mail.app 10.3.9 to Tiger conversion help

[Scott Ehrlich]

I have a user using mail.app with an IMAP server.  I took their 10.3.9 
machine out of service after backing it up, in full, to an external 
firewire drive.

I put in a newer machine running Tiger, fully patched, and copied their 
10.3.9 mail.app folder, with all mailboxes, over the new mail.app mailbox.

Upon checking mail, the server still insists on pushing all 20,000+ 
messages on the server back to her machine.   How can I, if possible, do 
the same as above, but have the server only download a diff between what 
her backed up email folder has to her new email, and simply download the 
new stuff?

Thanks.

Scott