Resolved - it was indeed a lookup problem. Thx!
-----Ursprüngliche Nachricht----- Von: owner-postfix-us...@postfix.org <owner-postfix-us...@postfix.org> Im Auftrag von Gerald Galster Gesendet: Samstag, 21. August 2021 11:09 An: Postfix users <postfix-users@postfix.org> Betreff: Re: Hostname DNS error > Aug 21 10:22:59 stretch postfix/smtpd[8394]: warning: hostname > mail.radio-z.net does not resolve to address 136.243.54.124 Aug 21 > 10:22:59 stretch postfix/smtpd[8394]: connect from > unknown[136.243.54.124] Aug 21 10:22:59 stretch postfix/smtpd[8394]: > 18D3F6A40A2B: client=unknown[136.243.54.124] > > The reverse DNS for that host is set (IPv4 and IPv6) and seems to work. In case you use the standard resolvers provided by your data center, you could install a local resolver like unbound. /etc/resolv.conf: nameserver 127.0.0.1 Best regards Gerald
