Gmail has several options for storing and categorizing your email, including a star system that allows you to mark important emails. You can search your email based on the different available categories, including which emails are starred and which are not. Once you have all the unstarred emails loaded on the screen, you can use a shortcut to delete all of them at once.
Sign in to your Gmail account.
Type "-is:starred" in the search box near the top of the screen and click "Search Mail." The "is:starred" search operator displays all your starred emails. Placing a "-" in front of it reverses the search and displays all your unstarred emails.
Press the black, down-facing arrow next to the blank box, and select "All." The blank box is located to the left of the "Archive" button above your email listing. All the emails in the list are highlighted. Note that the message "All 20 conversations on this page are selected" appears above the first email in the list.
Click "Select all conversations that match this search" next to the "All 20 conversations on this page are selected" message. The message "All conversations in this search are selected" replaces the original message.
Select "Delete" from the row of buttons above the email list. The message "This action will affect all conversations in this search. Are you sure you want to continue?" appears on screen.
Click "OK" to delete all the messages.
You can restore all your emails immediately by clicking "Undo" next to the message "All conversations have been moved to the trash."