[Mimedefang] Validating sender domain opinion

[Steffen Kaiser]

Hello,

there has been talk on the list placing 127.** or some other private 
address as tarpit as MX record with least precedence.

What about a DNS configuration with an invalid private MX as first one?

I just test a sender validation by grabbing all MX's records and check if 
the first one is an external address; doing so I found this domain:

; <<>> DiG 9.2.4rc5 <<>> -t mx mox.de.
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29441
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 2, ADDITIONAL: 4

;; QUESTION SECTION:
;mox.de.                                IN      MX

;; ANSWER SECTION:
mox.de.                 252     IN      MX      30 mail.portunity.de.
mox.de.                 252     IN      MX      10 192.168.100.251.
mox.de.                 252     IN      MX      20 mail.mox.de.

These are not spammers, BTW.

I would consider such setup invalid and my code had rejected the mail, if 
it were enable. -- I mean, why does they try to deliver mail to one of my 
hosts, private addresses are "my hosts", aren't they?
I ignore the fact here intentionally, that they do point to a numerical 
address rather than a symbolic host.

What do you think?

Bye,

-- 
Steffen Kaiser