exchange 2k3 horrible failure recovery

Say you are the poor bastard that gets stuck fixing someone's horrible screw-up of a server migration involving an exchange 2k3 server. Say they decide to recreate the ad entirely and don't use the same domain name or information. What are you to do when someone wants to get their 3+ gb of existing mail back? Well if your original server is toast and your backups aren't quite up to snuff, but you happen to have the mdb files you can attempt to force the server to load your old files using legacydn. Once you've gotten the files loaded, you can export the mailboxes using exmerge.

Stop the unmount the mdb and stop the information store so you can backup the new datafiles. Copy over the old datafiles and start everything up. The files will not immediately be loaded, attempt to load them once and then hit the event log to get the error information. The information store will be the service in question, you should find a message regarding /O=old_org_name/OU=old_site_name/CN=RECIPIENTS/CN= does not match the DN of directory /O=new_org_name/OU=new_site_name/CN=RECIPIENTS/CN=.. Keep the new information stored somewhere, because you'll need to put it right back in after you're done exporting the old mail. You will need to create new temporary users for each user if they were already created in the new domain and linked to a new mailbox. I suggest you use the same name/information adding "Tmp" to the last name and username, this will allow you to use exmerge to mass export/add. Each mailbox will need to be connected to a matching temp user account, using the recovery tools.

Assuming you successfully exported all of the old user email, your going to want to return the directory to its original state. After you've done that, stop the information store and pop the original data files back into place. Fire everything up again, and you should be able to mount the new mdb. Use exmerge to import all of the mail and you're done, don't forget to delete the temp users (I'm pretty sure anyone reading this doesn't need me telling them that, but just in case). Good luck.