Manually Delete All

Warning! These steps will delete ALL items in your Sent folder. 

The instructions below are for Gmail.  

Step 1 - Go to:  mail.google.com (you cannot do this from the Gmail smartphone app)

Step 2 - Sign in to your Gmail account.

Step 3 - Click the "Sent" folder

On the main Gmail account page, click the "Sent" folder option.

Step 4 - Select all items currently displayed in Sent folder

Step 5 - Click the option to select ALL messages in the Sent folder.

Step 6 - Click the "Trash" icon to delete all selected messages.

Step 7 - Click the "Trash" folder and click "Empty Trash now".