Importing Mail Mailboxes after a clean installation of Lion

Question

I have had to re-install Lion (10.7.3, a clean installation). I have now been able to download messages still on my Internet provider's server, but how can I transfer them from my bootable cloned copy of my entire system, made just before re-installing the OS?
Mail offers to export messages (Mailbox >Export Mailbox). Could I boot on my cloned backup, export each mailbox, then in some way import them into the new Lion system?
But my Mail's File > Import Mailboxes is greyed out, and Apple's Help ("Import mailboxes" doesn't work).
Or could I drag the old mailboxes from the backup, but where are they?
I have a Time Machine backup which will have the messages, but again, where? I mounted TM, tried Mail > Import Mailboxes and selected the Mail application. TM whirred for ages and I eventually had to force quit mail after the SBOD appeared.
Hoping for some ideas.

Answer 1

If you are installing from the DMG, I think so.   However, once installed to a hard drive or flash drive as a bare bones bootable 10.7 system the only time an internet connection would be needed is if you have Software Update setup in System Preferences, or Quicktime setup in System Preferences for updating your software.
You can setup a clone software on that bootable drive such as Superduper or Carbon Copy Cloner that can get you off the ground and running to verify that you aren't having any hardware issues with your system, instead of trying to eliminate software issues on a fully loaded 10.7 system.
Of course you'd want two clone backups of your fully loaded system before you tried that.  A Time Machine backup of your fully loaded system can work too, as long as it is to a hard drive that is at least twice as large as the original.
The only reason to keep the DMG version of it around is if you lack the space or funds for space to have a fully installed backup.  But then you are depending on the internet anyway!