Login to your electronic mailbox.
Open the folder "Trash", "Deleted items" or equivalent folder where deleted emails. The folder name depends on the service of providing electronic mail services.
Look in the folder you are interested in writing. To facilitate the search you can use the button "Sort". In this case, a popup window will appear where you can choose the way of sorting: by date (newest first/oldest first), author (A to z/z to A), topic (from A to z/z to A).
Find the appropriate letter and mark it for restoration. For this box next to the heading of the letter you need to put a "tick" and click on the button "Move", selecting the folder to move.
After done action open the folder to which you moved the selected letter, and find him.