[Novalug] Hosting email

Derek LaHousse dlahouss@mtu.edu
Sun Dec 18 23:06:02 EST 2016


Requesting clarification because I might learn something:

On Sat, Dec 17, 2016 at 4:19 PM, Rich Kulawiec via Novalug
<novalug@firemountain.net> wrote:
> (Again, one of the
> simple/fast/efficient things is enforcing FCrDNS checks.)
>
> ---rsk

Since I had to look it up, I'll TL;DR for everyone else... FCrDNS is
"Forward-Confirmed Reverse DNS", which I've understood to mean that
the IP matches the hostname matches the IP.  In the case of
mailserver, the box trying to send mail has a name which matches the
IP, and all that matches the domain on the MAIL FROM.

Rich, you've railed against SPF in the past.  Spammers were the first
to set it up and it's meaningless because people screw up their
entries (particularly softfail).  But here we have what appears to be
the same mechanism.  Is it simply that the crap-mail outfits that are
so bad at other aspects happen to get this one right enough to make it
of value?  Or is there a qualitative difference I've failed to
understand?

To restate, why does "Thou shalt listen to no mailservers but these"
fail so bad when "this computer is in my domain and I know about it"
is successful?

Thanks for sharing your knowledge.



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