Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550-Message rejected because mail-wy0-f171.google.com [18.104.22.168] is
550-blacklisted at safe.dnsbl.sorbs.net see Currently Sending Spam See:
550 http://www.sorbs.net/lookup.shtml?22.214.171.124 (state 14).
Hier kann man also nicht von einer Gmail-Adresse an eine andere Gmail-Adresse Email schicken weil....Google in der SORBS Blacklist ist wegen Spam.