Since version 6.9.9 (and up to version 7.0.1) some subscribers do not received emails because they are rejected for spam policy. That concern users with email managed by sfr.fr.
SMTP error from remote server for TEXT command, host: smtp-in.sfr.fr (18.104.22.168) reason: 550 5.7.1 Email rejected per SPAM policy
Everything works fine if I switch back to version 6.9.8.
Is it possible to know what has been changed since version 6.9.9 that can cause this problem.