With this tool, you can search through selected folders for given criteria that can be set to match against the various header and body fields of an email.
Choose the folder you wish to search, enter the search criteria, and then select the part of the message to search. When you submit, the list of messages appears below the search form. You can choose the message you wish to view, and read it in the same way as a normal message.
Please note: when you are reading messages and then go into the search section, your currently active folder will be the default to search through. For example, if you were browsing through your ‘Draft’ folder and then clicked on ’Search’, ‘Draft’ is automatically selected for searching. If you want to search a different folder, then you must actively select that folder from the dropdown list.

To the left of the input field, there is a dropdown list of different parts of messages that are possible to search through:
Please note: when searching the 'From' field, you may receive some search results that do not seem to match the search criteria. This is because a normal ‘From’ field includes the name AND email address, but SquirrelMail usually only displays the name. If your criteria matches the email address, even though it is not displayed, that message will still be returned as a match.

If you have enabled this option, the Search page also displays an overview of up to nine of your most recent searches for quick access. Click on the Search option next to the listed search to perform it again.
With the Save link you can move a search to the Saved Searches which will be kept until you explicitly press Delete.
Click Forget to remove a search from the list of recent searches.