You have the option to delete your account with Plain English and all data associated with it (including the emails you receive).
Cancel a paid subscription: See this article to cancel a paid subscription without deleting all your data.
To request that we delete your account and all your personal data:
Log into PlainEnglish.com (so we know which account is yours)
Go to the Contact page
Choose "Delete my account & all data" from the dropdown
Click "Submit" (a comment is not necessary)