X1 Search vs Lookeen: Which Outlook Search Tool? (2026)

X1 Search and Lookeen both put a fast keyword index over Outlook on Windows, and both search your files as well, so they land on the same shortlists. They differ in how they are sold and how far they reach. Lookeen sits inside Outlook as a plugin, costs from €9 per user per month billed yearly, and adds an AI assistant built on ChatGPT models. X1 Search is a separate desktop application at $79 a year that reaches across Microsoft 365, Slack and other mail accounts. Here is how they compare, checked against both vendors' pages.

Disclosure: Inbox Search is our product, and it appears near the end of this comparison. X1 Search and Lookeen details come from x1.com and lookeen.com, checked on November 3, 2026. Prices and features change, so treat the vendors' own pages as authoritative over this one.

The short answer

• Choose Lookeen if you want search inside classic Outlook, across emails, appointments, tasks, notes and contacts plus your desktop files and network drives, from a vendor that develops in Germany and offers an on-premise server edition.
• Choose X1 Search if your information is spread across Microsoft 365 (Teams, SharePoint, OneDrive, the Online Archive), Slack or several mail accounts, or you need deep metadata filters.
• Choose neither if you use a Mac or Outlook on the web: both are Windows-only.

What do X1 Search and Lookeen cost in 2026?

The two price differently: X1 by licence, Lookeen per user per month, billed yearly. As of November 3, 2026:

Lookeen's prices include VAT and come with a 14-day trial. Its three desktop plans include the same Outlook, Exchange and PST search; what rises with the price is mainly the AI assistant's daily allowance (see below). X1 also offers a 14-day trial, prices volume and enterprise licences through its sales team, and was showing a 20% discount on its purchase page when we checked.

For one user, X1's yearly licence costs less than Lookeen's cheapest plan. For a team, ask both for a quote: X1's volume licences and Lookeen's Server edition are both priced on request.

Inside Outlook, or beside it

Lookeen integrates into Outlook as a search plugin, so you search from within classic Outlook, and it doubles as a desktop search tool for your files. Its pricing page lists the Outlook add-in for Outlook for Microsoft 365, 2024, 2021, 2019 and 2016, and Exchange Server 2010 SP2 to 2019 in cached and uncached mode. It does not mention the new Outlook for Windows or Outlook on the web.

X1 Search is a separate application with its own window. It reads your mail through its Microsoft 365 integration and from PST files, and lists Exchange, Outlook, the Online Archive, and contacts and calendar among its Microsoft 365 sources. Its page does not name the new Outlook either.

In practice: if you live in classic Outlook and want search where you already work, Lookeen fits that habit. If you want one window over many sources, X1 is built that way. If you use the new Outlook, test either one during its trial before paying.

What each one searches

• Lookeen searches emails and attachments, appointments, tasks, notes, contacts and calendar entries; local PST and OST files and public folders; and files on your desktop and network drives, "in all common formats", in its words. Its feature table also includes Online Archives, on some plans, so check which before you buy.
• X1 Search searches Microsoft 365 (Exchange, Outlook, the Online Archive, Teams, SharePoint, OneDrive, contacts and calendar), Slack, Gmail through an API connector, Yahoo, AOL and other IMAP accounts, PST files, local files and file shares, Google Drive, Box and Dropbox.

Both cover the classic case of Outlook plus files. X1 goes further into chat, cloud and other mail accounts. Lookeen goes deeper into Outlook's own items, such as tasks and notes, and into public folders.

Search and filters

Both are keyword tools at heart, and both are quick once the index is built. X1 offers search as you type, hit highlighting, previews of files in their native format and more than 50 metadata filters. Lookeen offers advanced queries and filters across Outlook's fields, from the search box inside Outlook.

What neither does in its everyday search box is find an email by meaning. If you remember what an email was about but not how it was worded, a keyword index has nothing to match: "expense report" will not find "reimbursement form".

AI features and privacy

• Lookeen's AI assistant summarises emails, drafts replies, finds key points, spots contradictions, builds timelines and extracts email addresses. It runs on ChatGPT models with a daily allowance per plan: Basic 10 GPT-4o mini and 2 GPT-4o queries a day, Business 10 and 10, Premium 100 and 30. The Server edition is unlimited with your own API key.
• X1 Search uses AI to classify and tag emails, documents, chats and attachments, which X1 says improves relevance and helps identify sensitive information. It recommends 16 GB of RAM and a dedicated Nvidia or AMD graphics card for its AI features.

Both build their search index on your PC. Lookeen, developed in Germany, states that "no indexed information is sent to the internet". Its site does not explain how the AI assistant's ChatGPT queries are handled, so ask Lookeen if that matters for your mailbox. X1 says its AI models are applied "within your environment".

Platforms and setup

• Both are Windows-only. X1 lists Windows 10 and 11 and says Mac and Windows on Snapdragon (ARM) processors are not supported, with no Mac release imminent. Lookeen lists Windows versions only.
• X1 asks for more of the machine: 8 GB of RAM and 20 GB of free storage as the base, and the AI recommendation above.
• Lookeen offers more ways to deploy: on the desktop, on an on-premise server or in a private cloud.

X1 Search vs Lookeen at a glance

When neither is the right tool

X1 and Lookeen solve the same problem in the same way: an index on a Windows PC, matched on keywords. If your problem is a different one, so is the answer.

• On a Mac or in a browser. Neither runs there.
• On the new Outlook for Windows. Neither vendor names it, so you would be relying on a trial to find out.
• Searches that fail on wording. If the sender wrote "Your stay is confirmed" and you search for "hotel reservation", a keyword index has nothing to match.

Inbox Search is an Outlook add-in built for those cases. It finds emails by meaning entirely on your device, and because it runs inside Outlook rather than beside it, it works the same in the new Outlook and classic Outlook on Windows, in Outlook for Mac and in Outlook on the web. It combines semantic search with keyword matching, so exact terms such as an invoice number still come first, and its AI model was trained on more than 50 languages.

It does less than either tool above in one respect: it searches email in your primary mailbox only, with no files, no shared mailboxes, no public folders and no Online Archive. Keyword search and indexing are free and unlimited, with 5 AI finds a day; Pro removes the limit for €7.99 a month or €79 a year, VAT included, with a 7-day free trial (see pricing).

Which one should you pick?

• Classic Outlook, Outlook's own items and your network drives, in one place: Lookeen.
• One search across Microsoft 365, Slack and several mail accounts: X1 Search.
• The lowest yearly price for one person on Windows: X1 Search, at $79 against about €108 for Lookeen Basic.
• Only email, on any platform, or searches that keep failing on wording: Inbox Search.

All three have free trials and none of them changes your mailbox, so the fairest test is to run two side by side and search for five emails you struggled to find recently. For more detail on each, see our Lookeen alternatives, X1 Search alternatives and the comparison of the best Outlook search tools.

Frequently asked questions

X1 Search vs Lookeen: which is better? Lookeen suits people who want search inside classic Outlook, across emails, appointments, tasks, notes and contacts plus desktop files and network drives. X1 Search suits people whose information is spread across Microsoft 365, Slack and several mail accounts, or who need deep metadata filters. Both are Windows-only, and everyday search in both is keyword matching.

Is X1 Search cheaper than Lookeen? For one user, yes. X1 Search costs $79 a year, or $237 for three years, often promoted to $189. Lookeen costs 9, 12 or 25 euros per user per month, billed yearly, so about 108 euros a year on its cheapest plan, VAT included. For teams, both price volume licences on request.

Do X1 Search and Lookeen work on a Mac or in Outlook on the web? No. As of November 2026 both are Windows-only. X1 says no Mac release is imminent, and Lookeen lists Windows versions only. Inbox Search is an Outlook add-in, so it runs in Outlook for Mac and Outlook on the web as well as on Windows.

Do Lookeen and X1 Search use AI? Both do, differently. Lookeen has an AI assistant for summaries, replies and key points, running on ChatGPT models with a daily quota per plan. X1 Search uses AI to classify and tag content, and recommends a dedicated graphics card for it. In both, the everyday search box searches a keyword index.