To list status of the index:
$ sudo mdutil -s -a
/:
Indexing enabled.
/Volumes/HDD:
Indexing enabled.
To erase and rebuild index:
$ sudo mdutil -E /Volumes/SSD
/:
Indexing enabled.
The search spotlight icon in the corner of your mac will have a little dot.
After the rebuild outlook will start to return all the results for email searches.