- NO: You can't stop them sending a message since that happens on their account not yours.
- NO: You can't stop Gmail from receiving the message on your behalf as that happens before it hits your account.
- YES: You CAN decide what happens AFTER Gmail delivers it to your account using the options available in filters.
- YES: You CAN use Google Apps Scripts to perform more advanced functions.
- REPORT: Report a user violating Gmail's policies.
Delete Messages Filter
This creates a filter that deletes messages from this user on receipt.
If you want to delete these messages on receipt rather than seeing them in SPAM or INBOX.
- Login to your Gmail account in a web browser.
- Naviagte to the filters tab in Gmail settings: https://mail.google.com/mail/u/0/#settings/filters
- Click on the Create a new filter link on that page.
- Enter the information that uniquely identifies the emails you want to delete. e.g. put the person's email address on the From line. firstname.lastname@example.org
- Once you have the identifying information in click the Create filter link
- check the options that apply which in this case would be (a) Delete it and (b) Never send it to Spam
- Click the Create filter button.
Note: Messages will be sent to your TRASH folder and permanently deleted in 30 days. There is no way from the GMAIL filters to permanently delete messages.
Google Apps Script
GAS is a way to perform all sorts of wonderful things in Google apps that aren't supported in the default Apps/GUI's. However, it requires a little to a lot of programming knowledge depending if you are just duplicating someone else's code or doing something new.
GAS would allow you to permanently delete the messages (and all your other messages too if you make a mistake ;-)
Report to Google
Google information on abuse: https://support.google.com/a/answer/178266?hl=en
Google info on reporting Phishing: https://support.google.com/mail/answer/8253?hl=en