[Evolution] How to transfer from new Evolution (and new format) to old?

[Fayer Michael <fayer012 gmail com>]

I need to transfer all my emails from one laptop (Ubuntu 11.10) to
another (Ubuntu 10.04).

On the 11.10 laptop, Evolution is 3.2.1 with new email format. I forget
the format name when I was asked to convert. The name seems to be ~6
letters long. Hundreds of files are in folder
'/home/xxx/.local/share/evolution/mail/local/cur'. They have similar
names. One of them is '1317082821.2435_1.roro:2,S' with size 9.6 MB.

On the 10.04 laptop, Evo is 2.28.3 which came with Ubuntu and no
settings were changed. So the format should be mbox (?).

I used the menu 'Back up Evolution Data...' in Evo 3.2.1 to create a
'*.tar.gz' file. But Evo 2.28.3 failed to read it using menu 'Restore
Settings...'. The error was 'Please select a valid backup file to
restore'. And I couldn't find other ways to transfer.

Any comments are welcome. Thanks in advance.