The problem is as follows:

SPF client does a request for 23.90.102.86.spf.hc2437-76.eu.iphmx.com
Server at iphmx.com responds with 127.0.0.2
Firewall between SPF client and server, drops the response packet with "UDP WAN 
DROP: DNS Rebinding protection"
SPF client gets a "timeout" to the response and thus fails the lookup.

If the response would be a non-private adress like 23.90.102.86, firewall 
wouldn't touch it.

-----Ursprungligt meddelande-----
Från: John Levine via mailop <[email protected]> 
Skickat: den 17 juni 2025 19:33
Till: [email protected]
Kopia: [email protected]
Ämne: Re: [mailop] iphmx.com - who owns that server (SPF fault)

It appears that Alessandro Vesely via mailop <[email protected]> said:
>On Tue 17/Jun/2025 10:10:47 +0200 sebastian wrote:
>> 
>> The thing is that iphmx.com seems to be a MaaS infrastructure who tells 
>> clients 
>> to use exists: as SPF records.
>> 
>> Like: exists:%{i}.spf.hc2347-76.eu.ipmx.com
>> 
>> One example:
>> 
>> 23.90.102.86.spf.hc2437-76.eu.iphmx.com
>> 
>> The problem is that these resolve to a private IP (172.0.0.2) which causes 
>> SPF 

When I try it I get 127.0.0.2 which is a localhost address.

That seems fine for exists: since the name exists.  Perhaps you could give us
more details of your failure scenario.

R's,
John
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