Normally when you delete Gmail messages they are moved to your Trash folder. Then, approximately after 30 days, they are automatically deleted. Once they are deleted from their Trash folder, these messages are permanently deleted.
But what if you want to delete some Gmail messages permanently immediately? Like, right now?
Instead of a single step, you may have to follow a couple of steps.
Go to your Gmail inbox folder, and select the messages that you would like to delete permanently.
You will notice as you select messages, some icons begin to appear in the top portion of your inbox.
Click the “Delete” icon highlighted by the arrow in the above image and all the selected messages are moved to the Trash folder. After doing this, on the left-hand sidebar, find the Trash folder and click it.
Sometime you may have to scroll the left-hand side links way down in order to go to the Trash folder and you may even have to click “More” in order to find it.
Select all the messages that you want to delete permanently and then click “Delete forever”. This way all the Gmail messages that you want to delete permanently, are deleted.