My Smart Mailboxes aren't showing messages

First check the case function

At the moment smart mailboxes are case sensitive, i.e., it matters whether you search with upper case or lower case letters. You can make a case insensitive search (i.e., a search where it doesn't matter if letters are upper or lower case) by using the following terminal command:

         defaults write ca.indev.MailTags performCaseInsensitiveComparisons 1

Then check Spotlight

It may also be that Spotlight needs to be updated for your messages data. Usually this occurs automatically when you tag a message, but if may not happen in some circumstances.

Fortunately updating the spotlight database for your all your tags is straightforward.

               - Open preferences
               - Select the MailTags preferences.
               - Select the Messages Tab
               - Click on Re-Index Tags

This will take a few minutes as it rebuild the tag data for spotlight.

The above technique will reindex all your messages.

If you want to reindex messages in a specific mailbox, just select the Mailbox and choose the Reindex MailTags from the Message Menu.

A problem with Spotlight

The problem may be with Spotlight itself. You can test this in the following steps.

     - Create a text edit document and type a unique word or 
       combination of letters, for example, XYZZY
     - Save the document with the name SpotlightTest
     - Do a system wide spotlight search (magnifying glass in top right)
       for the word

If the document doesn't show up then it would appear that Spotlight is not indexing properly.

To fix Spotlight

1. Try restarting the computer.

2. If this doesn't work, try rebuilding the Spotlight database.

     - Go to "Open System Preferences" and select "Spotlight Preferences"
     - Click on the privacy tab and add your Hard Drive to the privacy list
     - Close System Preferences and open it again
     - Drag the Hard Drive out of the privacy list and Spotlight will start 
       reindexing your harddrive
   

This process deletes the existing spotlight index and creates a new one. Since Spotlight merely indexes existing data, replacing it will not result in any data loss.