How to bounce email
The bounce feature is a tool which bounces an email back to the sender that indicates your email address no longer exists.
On the preview pane of each email, you'll see a link 'Mark for bounce'. Clicking this link will change the color of the email text to grey, and when you press the 'Wash Mail' button, the message will be bounced back to the sender so they receive a message that your email address does not exist. You can also use the 'B' key on your keyboard to mark an email for bouncing.
If the sender receives your bounced message, they should take you off their email list and not send you any more email. This is more likely to happen for companies who regularly clean their lists, but more often than not, will not work for spammers who mostly use fake email addresses.