Create Email
The Apple Mail program lives in the Application folder.
Cmd-Tab to Finder, File -> New Window -> select Application folder -> look for Mail
When in Doubt, Quit mail, wait, Start Mail again.
Searching Email :
Searching can be slow if numerous other applications are open. When in Doubt, Quit other applications.
Remember, it can be slow.
Also, try to avoid selecting any "hints" provided under the search field.
Be sure to search "all folders", and again, wait a while for the results.
Reading Email :
The best habit is to check email twice a day, and read all email. This means all numbers, next to mailboxes are less than 1.