You can mark the email in the checkmark box to the left of the subject line, go to the menu at the top (where you can reply etc) and click Mark As Spam. Then, emails from that email address will go into the spam folder and when you see that there are unread emails in the spam folder, you don't even have to open them-- you can click the little trash can next to the folder title and delete all your spam emails at once
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You can mark the email in the checkmark box to the left of the subject line, go to the menu at the top (where you can reply etc) and click Mark As Spam. Then, emails from that email address will go into the spam folder and when you see that there are unread emails in the spam folder, you don't even have to open them-- you can click the little trash can next to the folder title and delete all your spam emails at once