Understanding Exchange Search

Microsoft Exchange Server 2007 will reach end of support on April 11, 2017. To stay supported, you will need to upgrade. For more information, see Resources to help you upgrade your Office 2007 servers and clients.


Applies to: Exchange Server 2007, Exchange Server 2007 SP1, Exchange Server 2007 SP2, Exchange Server 2007 SP3

Microsoft Exchange Server 2007 Search is a feature that allows you to quickly search text in messages through the use of pre-built indexes. By using the Microsoft Search indexing engine (MSSearch), Exchange Search creates the initial index by crawling all messages in mailboxes within an Exchange 2007 database. As new messages arrive, Exchange Search updates the index based on notifications from the Microsoft Exchange Information Store service.

Exchange Search (also known as full-text indexing) allows your users to perform full-text searches across documents and attachments in messages that are stored in the mailbox database. Full-text indexes are not stored in your Exchange databases. The search index data for a particular mailbox database is stored in a directory that resides in the same location as the database files. By default, Exchange Search is enabled for all new mailbox databases. Typically, indexes occupy approximately 5 percent of the total mailbox database size, so it should be safe to allocate 10 percent of the total mailbox size for the indexes.

Improvements Over Exchange Server 2003 Content Indexing

The search functionality in Exchange Server 2003 (content indexing) is replaced with Exchange Search in Exchange 2007. Exchange Search provides the following feature and functionality improvements over content indexing:

  • Utilization of system resources such as CPU, memory, disk I/O, and disk space required for its indexes is improved, which significantly increases overall performance.

  • New messages are typically indexed within 10 seconds of arrival, and query results are returned within seconds.

  • Exchange Search is automatically enabled upon installation and does not require any configuration.

  • Attachments can now be indexed. Several attachment types are supported, including Microsoft Office documents, text attachments, and HTML attachments.

  • Indexing is automatically withheld for a specific mailbox database, which reduces the disk I/O load. Also, indexing is automatically withheld for the entire Mailbox server, which reduces both disk I/O and CPU utilization for Exchange Search.

  • There is an easily accessible search bar in Microsoft Outlook Web Access 2007 and query builder support in Microsoft Office Outlook 2007.

Exchange Search and Attachments

Depending on the version of Outlook you use, Exchange Search can search within attachments as well. The following list shows how you can use various versions of Outlook to include attachments when searching:

  • Outlook 2007. Use the Instant Search feature or Advanced Find to include attachments in your search. For more information, see Find a message or item by using Instant Search in Outlook 2007 Help.


    You must be in online mode to include attachments in your search.

  • Outlook Web Access 2007. By default, Outlook Web Access 2007 includes attachments in any text search.

  • Outlook 2003. Use the Find or Advanced Find features, with the Subject Field & Message Body box selected to include attachments in your search.


    You must be in online mode to include attachments in your search.

  • Outlook 2000. Use the Advanced Find feature (with the Subject Field & Message Body box selected).

Exchange Search allows you to quickly search text in messages through the use of pre-built indexes. Exchange Store Search, however, is based on a sequential scan of all the messages in the search scope instead of using the pre-built indexes The following list describes some of the other differences between Exchange Search and Exchange store search:

  • Exchange Search is faster than Exchange store search

  • Exchange Search is based on words, phrases, and sentences. Exchange store search is based on a stream of bytes. This means that Exchange Search will ignore punctuation and spaces, and is also not case sensitive, whereas Exchange store search will find only an exact match of all characters.

  • Exchange Search searches within attachments types that are supported by the installed filters. Exchange store search does not search within attachments.

  • Exchange Search uses its full-text index to locate records. Exchange store search performs a serial scan of the entire folder.

  • Exchange Search is not case sensitive. Exchange store search is case sensitive.

  • Exchange Search can be used only for text searches. Exchange store search supports the full set of MAPI restrictions, which includes non-text property types such as date and time.

In Outlook 2003 and later versions, users coan create either Online or Cached Exchange Mode profiles to access their e-mail messages. Using a Cached Exchange Mode profile allows users to work with their e-mail even when a connection to their e-mail server is not available. There are a several differences between Outlook Cached Exchange Mode and online mode search:

  • In Office Outlook 2007, Cached Exchange Mode search uses Windows Desktop Search, which is a prerequisite for the Outlook 2007 Instant Search(WDS 3.0) feature. If WDS 3.0 is not installed, Instant Search falls back to the Outlook 2003 model - a sequential scan of the entire search scope. Outlook 2007 in online mode uses Exchange Search if possible, and reverts to using Exchange store search if Exchange Search is not available.

  • In Outlook 2003, Cached Exchange Mode search does not use an index and runs on the client computer to sequentially scan every message in the search scope. Outlook 2003online mode search uses Exchange Search by using pre-built indexes, and reverts to using Exchange store search if Exchange Search is not available.

  • Cached Exchange Mode search uses an index that is built on the cached copy of the user’s offline folder file l (.ost) and runs on the client computer. Online mode searches occur on the server. While online mode searches have a performance impact on the Exchange server, they are likely to have better performance because they can utlilize the resources of a server instead of a client computer.

Exchange Search and Localization

Localization support for Exchange Search is limited to scenarios in which the client locale matches the message locale (which must also match the language that is used in the message body). Exchange Search does not support instances where a single message has multiple languages embedded in the body or where the client locale is different from the message locale.

To get consistent results for localized searches, the following must be true:

  • An e-mail message must be written in a single language and that language must match the locale of the message.

  • The search expression must be in a single language.

  • The language must match the locale of the client computer, as identified by the connection to the server.

Scenarios Where Exchange Search Could Return Unexpected Results

The following list describes some of the scenarios where Exchange Search returns unexpected results:

  • Documents that are encrypted with the Digital Rights Management feature will not be indexed.

  • For attachments that do not have associated filters, the attachment will not be indexed, but the e-mail message will be indexed.

  • Advanced search grammar (for instance, typing "From:xyz" in the basic search bar searches the from: property for the string "xyz") is supported only when Instant Search is enabled. Instant Search requires that Windows Desktop Search 3.0 is installed. For more information, see Windows Desktop Search.

For More Information

For information about managing Exchange Search, see Managing Exchange Search.