Without a proper search feature, every software dealing with a lot of data is doomed at the start. It is likely to be virtually impossible to manually navigate to the folder and to the specific item that you want, especially in email clients like Outlook. Therefore, a robust and friendly search feature in a client like Outlook is crucial. This article will shed some more light on how this feature works in Outlook desktop email client and how WDS (Windows desktop search) and ‘FAST’ search (used mainly in SharePoint) are also linked.

What are ‘WDS’ and ‘FAST’?
WDS: Windows desktop search is a feature in computers running Windows operating systems. So naturally, it is primarily used to search the local data, but there’s more to that. It is also referred to simply as Windows Search.
‘FAST’: It is primarily a search engine used by Microsoft for SharePoint collaboration (web-based) platform.
To simplify it further, ‘FAST’ is server assisted search and WDS is locally-assisted Windows search.
So, when you search something on Outlook desktop, which one is used?
It’s complicated. Depending on several factors, like if the Outlook is on offline mode or if the network is slow, or if the searched query is not applicable, the client can use either system depending on those factors. When Outlook is not connected to internet and you imitate a search, it uses Windows desktop search feature to look for the item you search. When it is connected to the internet (and the latency is not big enough), the latest versions of Outlook uses “FAST” to search the mailbox content directly.
WDS or ‘FAST’ in Outlook 2016 and earlier?
It must be noted that before Outlook 2016 version, the actual server mailbox content was never crawled or indexed. Therefore, anytime you search in client versions earlier than 2016, WDS is the one that is always used. It is done by indexing .ost and .pst files. When an exchange account is added to Outlook and is configured to use cached exchange mode, the content is indexed by Windows Search.
Outlook still uses Windows search but 2016 onwards, there is also the ‘FAST’ search functionality that can look up for items within the mail servers.
“The Windows Search Engine is Currently Disabled” Error!
There are scenarios where the default Windows Search Engine is either turned off manually or automatically by some program/service. If you try searching in Outlook if Windows search is off, you will first get a message box’ saying “The Windows search engine is currently disabled” and that you won’t get instant and quick search results. If you click ‘OK’ and continue with your search, this is when Outlook can also search online from the servers of your mail account using ‘FAST’ functionality.
However, there are certain categories of searches that are not applicable or supported by ‘FAST.’ In those cases, if the Windows search is off, you won’t get any result.
If you want to run the windows search service again, follow the steps below:
- Go to ‘Control Panel’ of your Windows PC à Open ‘Administrative Tools. Or, click on ‘Start’ and search by start typing ‘Administrative Tools,’ and open it that way.
- A folder with the shortcut for the administrative tools will open up. Find ‘Services’ and open it.
- Scroll down and look for ‘Windows Search’ service. Or quickly type ‘Windows Search’ to directly jump to that.
- Right click on it and click on ‘Start’ or ‘Resume,’ if in case it was paused.
Once this is done, you will notice that when you start searching in Outlook, the client will again start searching within .ost and .pst files (locally indexed files).
How to find out if the search results are through WDS or ‘FAST’?
- As mentioned above, without Outlook connected to internet, it is always WDS results you are seeing. If Windows Search service is not running, you will not see any results.
- With ‘FAST’ results, you will see at the bottom of the search results a ‘More’ link to show you more results. Initially, Outlook only displays the recent results searched within the servers using ‘FAST.’
- By clicking “More,” Outlook displays more of the results that it can find. You can see “Loading” at the end, particularly if internet is slow or latency is high. For some, it can take a lot of time, but after a while, you will see another message/link – “Let’s look on your computer instead.”
- When you click on ‘Let’s look on your computer instead,’ it is the WDS results that you will see. Interestingly, you will get another option and that is to look on the server, but this is done through a non-FAST query to the exchange servers even though it is not searching within the local database. A point must be noted here that Exchanged servers 2016 also supports legacy search functions to offer compatibility with Outlook 2013 and earlier versions.
Also Read: Adjust and Modify View In Outlook
How does this all information help you?
As the point made at the start of this article, without a proper search function, most software dealing with data can be made irrelevant and impractical. It is not efficient or even possible to manually navigate to an item you are looking for.
In fact, building search engines and developing search algorithms are interesting and lucrative domains that are constantly being at the center of attention of most software and administrators. Interestingly, Microsoft acquired a company called ‘FAST’ in 2008 based in Norway that specialized in data search technologies.
By understanding the search engines and how Outlook is searching your queries, you can better and more efficiently manage your work as an individual or as an administrator for a company.
Next time, we will discuss the options within Outlook that can tweak the searching and fine-tune it even further. We will also find out how to change the scope of search (within all Mailbox or all Outlook items or only current mailbox or something else) and how to set a search scope as default.