Whatever search you try with outlook App it shows no result.
Is probably because it passes

<CollectionId xmlns="AirSync:">0</CollectionId>

in the activesync request.

Request:
<!DOCTYPE ActiveSync PUBLIC "-//MICROSOFT//DTD ActiveSync//EN" "http://www.microsoft.com/&quot;>
<Search xmlns="Search:">
<Store>
<Name>Mailbox</Name>
<Query>
<And>
<Class xmlns="AirSync:">Email</Class>
<CollectionId xmlns="AirSync:">0</CollectionId>
<FreeText>something</FreeText>
</And>
</Query>
<Options>
<BodyPreference xmlns="AirSyncBase:">
<Type>2</Type>
<TruncationSize>1048576</TruncationSize>
</BodyPreference>
<RightsManagementSupport xmlns="RightsManagement:">1</RightsManagementSupport>
<RebuildResults/>
<DeepTraversal/>
<Range>0-49</Range>
</Options>
</Store>
</Search>

Response:

<!DOCTYPE ActiveSync PUBLIC "-//MICROSOFT//DTD ActiveSync//EN" "http://www.microsoft.com/&quot;>
<Search xmlns="Search:">
<Status>1</Status>
<Response>
<Store>
<Status>1</Status>
<Range>0-0</Range>
<Total>0</Total>
</Store>
</Response>
</Search>