Outlook Does Not Look up All Emails

You are searching for messages in your mail and you feel that there should be more emails found or the search returns only few results.

There may be several causes:

You typed the condition incorrectly, and there is no email matching the condition,
incorrectly selected search range,
there are only few results found, you feel that there should be more of them,
there is a corrupted index – it affects only Outlook

1. Wrong Condition or How to Write Conditions? [menu]

1.1 Conditions in Outlook [menu]

You can enter a number of phrases into the search box above the list of messages in Outlook.

Schoo	it is searched by first letters. Outlook finds messages containing School, schooling, schools and schooled (ignoring diacritics or case), but not preschool or homeschooler
schoo econ	it searches for messages in which the word starts with schoo and the word starts with econ. The order does not matter
“school”	it searches for the exact string, i.e. in the header, text or attachment – there must be exactly the word school found.
schoo NOT econ	it searches for emails containing a word starting with schoo and not containing a word starting with econ

More complex conditions can be added – e.g. according to the sender’s address, for what period, whether it contains attachments, etc. Options on the Search tab that appears upon starting your search may help you enter these conditions. >>>mail_14

1.2 Web Interface Conditions [menu]

In the web interface, entering conditions is slightly different:

School	words such as school or School (ignoring diacritics or case) are searched. Unlike in Outlook, the word schoolboy is not included
schoo* econ*	it searches for messages in which the word starts with schoo and the word starts with econ. Unlike in Outlook, you must enter the asterisk. The order does not matter
“school”	it searches the exact string, i.e. in the header, text or attachment – there must be exactly the word school found
schoo* NOT econ*	it searches for emails containing a word starting with schoo and not containing a word starting with econ

2. Search Range [menu]

By default, Outlook and the web interface searches the entire mailbox (both on the web and between the contacts). You can limit the search to a specific folder – you must select a folder to search through.

If you are browsing emails in a specific folder before starting the search, it is only searched in that folder – sometimes it may be confusing. When searching in Outlook, make sure that Current Folder or Subfolders or Current Mailbox are written next to the search box.

3. There Are Only Few Results Found [menu]

This may be due to an incorrect condition or an incorrectly selected range. However, two factors still affect the number of results:

The number of results found is limited. If there are more than 50-100, try refining the condition. In most cases, the following is displayed at the end of the search list: The search is complete. If you do not find what you are looking for, try typing again with more specific expressions.
Outlook searches first only in newer messages. Outlook for Windows has only downloaded mail locally for the last 3 to 12 months. And it searches first in these downloaded emails. At the end of the list, either the link Find More on Server or More appears – when you click on the link, Outlook searches for older messages on the server.

4. Outlook Index Error [menu]

Outlook returns the message: No results found even if a message with the specified string exists or Outlook returns a message The search results may be incomplete because items are still being indexed.

When you download emails to your local computer, Outlook also creates indexes to use when searching for messages. These indices can be broken e.g. in case of unexpected power outage.

For more information, see the article Outlook Search Returns No matches found.

5. More Information [menu]

Fixing Instant Search – English description including images.
Find a Message with Instant Search
How to Refine Your Search Criteria and Improve Your Outlook Search – the official description, unfortunately, contains inaccuracies. The article contains English keywords; in some cases it is necessary to enter Czech equivalents in the client in Czech language. E.g. instead of messagesize:> 5MB, it is necessary to enter velikostzpravy:> 5MB (in Czech).
Keyword Query Language (KQL) syntax reference – Web search rules apply not only to mail, but also to OneDrive or SharePoint
Keyword queries and search conditions for Content Search