Re: MTA

[Greg Wooledge <greg@wooledge.org>]

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.ricks@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.