http://qlh4rf4cqtn3vlqtxnr4jqo4aubpt2qqj5y3rg3n3yioc3rlk3fdbnid.onion/howto
Create a new e-mail address somewhere, just for this purpose, use that address exclusively for darknet activity (for example, regularly buying products from us), and forget/delete that address completely, if you think you're done with the Darknet.