SMTP Fehler (550): Der Absender "suabc123@mail.uni-kiel.de" konnte nicht gesetzt werden (Verification failed for <suabc123@mail.uni-kiel.de>
Previous (cached) callout verification failure
REJECTED - Sender Verify Failed - The return address you are using for this
email message <suabc123@mail.uni-kiel.de>does not seem to be a working
account.
(unknown sender address - unbekannte Absender-Adresse)).