Mail provides an easy way to search for messages.
Just click the Search link on the left-hand navigation bar. If you are not sure of the exact spelling, use asterisks in place of the letters you're not sure about. If you have an idea when the message in question might have arrived, limit your search by date to make it faster and more accurate. You can also improve speed and accuracy by limiting your search only to certain folders. If the above steps have allowed you to enter enough information, click the Find Message button to start your search.