On Mon, Jul 05, 2021 at 09:23:03AM -0400, Polyna-Maude Racicot-Summerside wrote: > Reporting-MTA: dns; premium58.web-hosting.com > > Action: failed > Final-Recipient: rfc822;bjoern.ri...@greenbone.net > Status: 5.0.0 > Remote-MTA: dns; mail.greenbone.net > Diagnostic-Code: smtp; 550 X-Host-Lookup-Failed: Reverse DNS lookup > failed for 162.213.253.79 (failed)
unicorn:~$ host 162.213.253.79 79.253.213.162.in-addr.arpa domain name pointer cyrania.com. unicorn:~$ host cyrania.com. cyrania.com has address 172.67.185.109 cyrania.com has address 104.21.59.235 cyrania.com has IPv6 address 2606:4700:3031::6815:3beb cyrania.com has IPv6 address 2606:4700:3031::ac43:b96d cyrania.com mail is handled by 0 _dc-mx.f1202d9a4fb3.cyrania.com. Your "reverse" (PTR record for 162.213.253.79) doesn't match. Which is to say, none of the "A" results from cyrania.com. match the original IP address of 162.213.253.79. Some SMTP receivers may care about that. Apparently the receiver for greenbone.net (whose name is mail.greenbone.net) is one of them.
