We have received numerous report that in Mountain Lion Spotlight is not searching local HDDs. Since Outlook also uses Spotlight, no mailbox searching was possible either.
The fix is two-fold. The first thing to do is delete the index metadata:
sudo /rm ./metadata_never_index
Secondly, re-enable spotlight indexing:
sudo mdutil -a -i on
Technically simply turning Spotlight indexing ON using the mdutil command should resolve the problem. However we have found that you must first delete the index file first.
Update: We ran into a computer where the above steps did not resolve the indexing problem. On that machine the .metadata_never_index file was in the root volume (don't know why). Removing that file and then running "sudo mdutil -i on /" resolved the problem.
1. Double check that the .metadata_never_index file is not located at the root of the volume you are attempting to index
2. Disable spotlight indexing for the volume: sudo mdutil -i off /
3. Remove the index from the volume: sudo mdutil -E /
4. Remove the .Spotlight directory from the root if it exists
5. If there is a .Spotlight-V100 directory in the root, remove it: sudo rm -rf .Spotlight-V100
6. Enable indexing for the volume: sudo mdutil -i on /
