This is going to be a little bit technical.
User enters ********@ks-webstyle.de on facebook register form. Facebook checks if entered address can receive mail.
Postfix does sender verification (reject_unverified_sender), policyd-weight checks DNS, RBLs and some other stuff.
220.127.116.11 is listed in ix.dnsbl.manitu.net, oops! Overall rated as spam since some checks made this email look fishy: