Case 1: Retrieve deleted emails from Gmail Inbox
First thing you must do is Go to Trash Folder (Recycle Bin for Gmail) inorder to recover deleted messages from Gmail.
Suppose you have tons of messages in your Trash that you have not cleared from a very long time. Gmail provides you with an In-built search feature to find your mails.. Select Trash Folder. And type the keyword that is present in your email and you can easily search the deleted message from Gmail Trash Folder.
After you have found your Mail message from Gmail. You can either Right Click on the message and select Move to Inbox folder.
Alternate Solution is Open your mail present in Trash and remove the Trash Tag by Clicking on the Remove Tag (X) option. This will Automatically Move deleted emails from Gmail Trash to Inbox Folder.
If you have to Move multiple folders Select all the files a from Trash and click on Folder icon and select Inbox folder to move all the deleted emails to Gmail Inbox.
(Note: After 30 Days time period Gmail automatically empties Trash Folder)
Case 2: Retrieve Deleted Gmail Emails from Gmail Trash
This case arises when you have chose to permanently delete the data from Trash as well by hitting Delete Forever Option.
To recover permanently deleted Gmail messages you need to contact the Google Support Team in order to retrieve deleted messages. You need to visit the missing email web page of google as shown below and fill the form with all the detailed description describing your problem in the form.
Suppose you have tons of messages in your Trash that you have not cleared from a very long time. Gmail provides you with an In-built search feature to find your mails. Select Trash Folder. And type the keyword that is present in your email and you can easily search the deleted message from Gmail Trash Folder.
Case 3: Cannot Find the Trash Folder
There are possibilities that user cannot see the Trash Folder in Gmail. This happens because Trash Folder gets hidden due to certain reasons. You can redo the changes and view Trash Folder by changing some Settings to retrieve lost Gmail emails.
Select the Setting Tab on the top right corner of the Gmail Window. And choose the Label Tab.
Now Choose the Show Button on the Right side of the Trash Keyword as shown Below:
This will help to make Trash Folder visible on the left side of the screen and this will allow you to successfully recover deleted messages from Gmail.