Mail messages and attachments are automatically indexed before messages are deposited in a mailbox. Each mailbox has an index file associated with it. This index file is required to retrieve search results from the mailbox.
If a mailbox's index file becomes corrupt or is accidentally deleted, you can re-index the messages in the mailbox. Messages and attachments in all the user's folders are re-indexed.
Re-indexing a mailbox's contents can take some time, depending on the number of messages in the mailbox. Users can still access their mailbox while re-indexing is running, but because searches cannot return results for messages that are not indexed, searches may not find all results.
Select the account and in the gear icon select Edit. The selected account opens.
Click Reindex Mailbox on the account's tool bar. This opens the Reindex dialog.
Click Start Reindexing.
Caution: When you click Start Reindexing, the first action is to delete the existing index file. If re-indexing is cancelled before the re-index process is complete, the user's mailbox is partially indexed and searches may not return the right results.
Click OK, to close the dialog. Closing the dialog does not stop the re-indexing process. Re-indexing runs in background.
You can check the status of the re-indexing process at any time. Select the account and click Edit, then click Reindex Mailbox. A progress bar is displayed.