Outlook search is not finding emails that exist

Microsoft's documentation identifies several possible causes: where Outlook searches, an incomplete search index, a limit on the number of results, and older mail that is not stored on your PC. The fixes below follow that documentation, for classic Outlook and for new Outlook for Windows.

Why Outlook misses emails that exist

• The search scope is too narrow. Classic Outlook searches the Current Folder, a Subfolder, the Current Mailbox, All Mailboxes or All Outlook Items. A search in one folder does not look in the others.
• The index is not complete. For the mail synced to your PC, classic Outlook uses the Windows search index; with a Microsoft 365 or Exchange account it can also search on the server. While items are still being indexed, Outlook warns that search results may be incomplete.
• The number of results is limited. Classic Outlook can limit the results it shows to 250. When new Outlook finds too many results, older items may not be displayed.
• Older mail is not on your PC. In Cached Exchange Mode, classic Outlook keeps 1, 3 or 12 months of mail on the PC by default, depending on the size of the disk. Older messages stay in your mailbox on the server.

Fix it in classic Outlook

Rebuilding the index can take a long time, so try steps 1 to 4 first.

1. Widen the search scope

For your own mailbox, click in the Search box and choose Current Mailbox or All Mailboxes in place of Current Folder. To change the default, go to File → Options → Search. In a shared mailbox or an online archive, Microsoft advises searching with Current Folder, in the folder concerned.

2. Show more results, deleted items included

In File → Options → Search, under Results, clear Improve search speed by limiting the number of results shown. To include deleted messages, select Include messages from the Deleted Items folder in each data file when searching in All Items.

3. Check the indexing status

Click in the Search box, then select Search Tools → Indexing Status. While items remain to be indexed, results can be incomplete.

4. Make sure Outlook is indexed

Go to File → Options → Search and, under Sources, click Indexing Options. Microsoft Outlook must be listed under Included Locations. If it is not, select Modify, select the check box for Microsoft Outlook and click OK.

The Windows Search service must be running as well. In the Services app, double-click Windows Search, set the startup type to Automatic (Delayed Start), and select Start if the status is not Running.

5. Rebuild the index

1. Close Outlook, open Control Panel and choose Indexing Options.
2. Select Advanced.
3. On the Index Settings tab, under Troubleshooting, click Rebuild.
4. Choose OK. Windows warns that the index might take a long time to complete.

6. Keep all mail on your PC

In Cached Exchange Mode, Outlook indexes only the mail it keeps on your PC. To keep all of it:

1. On the File tab, select Account Settings, then Account Settings.
2. On the Email tab, select your Microsoft Exchange account and select Change.
3. Drag the Download email for the past slider to All. Older versions call it Mail to keep offline.
4. Select Next, then Done, close the Account Settings window and restart Outlook.

In new Outlook for Windows

New Outlook has its own search settings:

• Scope: go to Settings → General → Search and update the search scope.
• Too many results: older items may not be displayed. Filters narrow the search.
• Mail on the PC: go to Settings → General → Offline and choose a longer period under Days of email to save.
• Several accounts: Microsoft states that multi-account search is not currently supported in new Outlook.

Finding older emails

In classic Outlook with Cached Exchange Mode, a search can end with Showing recent results… More. Click More, and Outlook retrieves the matching older items from your mailbox on the server. Without a connection to the server, Outlook shows Server unavailable, followed by the number of months of results shown.

To search all older mail on the PC itself, set Download email for the past to All (step 6 above). In new Outlook, filters narrow a search for older results, and a longer Days of email to save keeps more mail on the PC.

Searching for an exact phrase or several words

Outlook's search box accepts a few operators. AND, OR and NOT must be typed in capitals.

• "expense reports", with the quotation marks, finds messages that contain the exact phrase.
• expense AND report finds messages that contain both words, not necessarily in that order.
• expense OR report finds messages that contain either word.
• expense NOT report finds messages that contain expense but not report.
• subject:report searches the subject only; from: followed by an address searches the sender.

Another way to search your mail

The steps above address the documented causes in Outlook itself. SearchFlow, a Windows application by DomusFlow BV, gives you a second route to the same mail: it reads your mailbox from Microsoft 365 and keeps its own index on your PC, so its results do not depend on Outlook's search index or on how much mail Outlook keeps on the PC.

• It indexes all your mail, however old, newest first, so you can search while the first index is still being built.
• Every folder of the mailbox is included, Sent Items and Deleted Items among them.
• Several Microsoft 365 accounts, also from different organisations, are searched in one list.
• Results appear while you type, and a result opens in classic Outlook, where you can reply or forward it.
• The same search covers the text of PDF, Word, Excel and PowerPoint attachments, and your documents in OneDrive, SharePoint team sites and the folders you add. See searching inside attachments and PDF files.

SearchFlow works with Microsoft 365 work or school accounts. An administrator of your organisation approves SearchFlow once; after that each employee signs in with a work account.