Migrate server mail files

I bought a new Mac mini server running MLS and restored all did a complete restore of the time machine backup of my broken SL Server. This restored everything under the MLS operating system but as you know broke a number of things - Sieve, mail authentication etc. Many of these I have fixed except for Sieve. I need some kind of Server side mail filtering for the users who only have iOS devices with no client filtering - plan was to use your Roundcube/manage sieve approach.

Secondly, I tried, using the second hard disk in the new server for now, to do a clean install and reset up the ML Server from scratch rebuilding a subset of users and then copying the mail store directories from the time machine backup of the SL Server to the new Server. I failed to find a way to associate the mail store directories and permission for the newly set up users. The server just built new mail stores and I could not find a way to transfer or combine them with the old mail stores.

Finally I tried the 'target disk mode' route to build an SL disk on an external FireWire drive that would boot the ML Server hoping I could just rebuild the original server on the new hardware. I used a CoreDuo Mac Mini we have to do the build but have so far not been able to get the new server to boot. It just hangs before getting to the log in screen. I have given up on this as I doubt I can ever get this stable enough with all the unsupported (by SLS) hardware in the new mini (e.g. Intel HD3000 graphics).

I have now run out of ideas on how o achieve my goal of a stable server, with my existing mail stores and users, with a server side spam filter. Any ideas are very welcome!

No - route 1 I tried was:

1. Clean install ML Server (new machine)

2. Migration assistant to restore data from SL Server time machine backup

Result was everything transferred (all important mail stores), broken mail client authentication (fixed), permission errors (fixed), domain and virtual domains broken (fixed), BUT no Sieve

Only one user (me, the admin) has a local user account on the server so not sure what would happen if I migrated users from the SL Server disk to a ML (without the Server app installed) and then install the app. I think I would end up where I did with route 2 and have the problem of merging the server mail stores when I add the users to the newly installed Server app? One difference maybe to try the migration from a rebuilt SL Server disk instead of Time Machine - to see if that makes a difference.

I have yet to give up on trying to get Sieve working or finding a way to merge server mail stores.