Strange constant message im mail.log: lost connection after AUTH from unknown

Anyone can help me understanding this message that keeps appearing in my mail.log: Dec 6 19:53:53 localhost postfix/smtpd[4873]: connect from unknown[185.234.219.94] Dec 6 19:53:53 localhost postfix/smtpd[4873]: lost connection after AUTH from unknown[185.234.219.94] Dec 6 19:53:53 localhost postfix/smtpd[4873]: disconnect from unknown[185.234.219.94] ehlo=1 auth=0/1 commands=1/2 I have fail2ban installed but it seems that is not block this…