I think I've figured it out, but it's neither automatic nor elegant - BOAC, take note
Spanners, you put me on the right track, I just didn't delve far enough into the import and export options to get past the first problem which is when you click on File|export|messages it will only export to a MAPI client on the same machine - Outlook or Microsoft Exchange. If you don't have one of those on that machine it won't work.
However, if you go to the other machine and select File|import|messages it is far more flexible and you can import from an OE6 store directory anywhere on the network.
BOAC, you put me on the right track there, I would never have found the store location without the example in your post.
You have to decide on a machine to be the "master", the other will be the slave. There are no boxes to tick, this is in your head. I chose the desktop as master, notebook as slave. On the master machine import the messages (choose All Folders - it's one of the options in the dialogue) from the slave. On the slave, delete all folders and contents (some folders won't delete, so delete their contents.) Empty the Deleted Items folder. Now import all folders and messages from the master. Done!
You have to empty the slave after importing from it because if you don't, all its documents will be duplicated as copies come back from the master. The import process is not smart enough to recognise duplicates and deal with them.
Then you have to import and export the address book. Funnily enough, address book import
is smart enough to recognise duplicate entries and asks you how to deal with them. First, on either machine export to a CSV file, then import on the other one. Then do it again, but swap the order of machines.
Like I said, not automatic, not elegant, but it works - nothing is simply overwritten, it is all merged and ends up the same on both machines.
fobotsco, I think your method would keep the Inboxes in synch, but I don't think it would deal with folders and folder contents that are different between machines, f'rinstance those that might have been created or changed on the notebook while it travelled.
Thanks for the tips, folks, you all helped get the grey matter churning.
AA