How to add Outlook 2013 to Indexing Options?

Question

Outlook

MS Office 2013 Pro is installed on the working computer (Win 7 Ult x64). Corporate mail - Exchange. From some point in Outlook, it became difficult to search for letters in the inbox. That is, everything I'm looking for is found, but for a long time. There are about 4 thousand letters in the folder, but the colleague next to him has 11 at all, but his search is performed quite quickly.
As a result, I found that Outlook is not in the Indexing Options list. I can't find clear information - how to add Outlook back to Index?