On 04/05/2016 11:33 AM, Andrew Morgan via Info-cyrus wrote:
On Tue, 5 Apr 2016, lst_hoe02--- via Info-cyrus wrote:
Zitat von Binarus via Info-cyrus <info-cyrus@lists.andrew.cmu.edu>:
Combine SPF / DKIM with domain blacklisting, and then you *have* an
efficient spam fighting tool.
As stated the spam actually reaching our inboxes after around 90%
cutoff is valid DKIM/SPF signed as it is mostly from the big free
providers like Outlook.com, Google and Yahoo. Some other big share is
from professional spam farms with always alternating IP and Domains
ranges from all over the world with also valid DKIM/SPF. Next big
share is from educational servers also mostly valid DKIM/SPF. The
tiny rest with around 10% is in fact not DKIM/SPF signed.
From the valid e-mail around 20% looks like having a valid SPF/DKIM,
mostly professional newsletters not personal mail from customers.
So No, SPF/DKIM is no useful spam fighting tool at least not in our
corner of the world.
Another recent standard, DMARC (https://dmarc.org/) allows the domain
owner to specify what the recipient should do with messages that fail
DKIM or SPF checks.
We ran into this recently and discovered that Yahoo's DMARC records
tell the recipient to REJECT messages that fail DKIM or SPF. Google
is honoring that DMARC record by putting the message into the Spam
folder.
This seems like a pretty effective method to prevent someone from
spoofing email from your domain. Of course, it does not prevent an
actual Yahoo account from sending spam, so you still need traditional
spam detection tools as well. However, it is nice that a third-party
sender cannot harm your domain's reputation through spoofing.
Note: I don't care whether this email list uses SPF or DKIM.
Andy
If you want to see flame wars even more pointless and/or entertaining
than this one, check out the mailing lists for DMARC. ;-) They make
these recent exchanges seem quaint by comparison.
_______________________________________________
dmarc-discuss mailing list
dmarc-disc...@dmarc.org
http://www.dmarc.org/mailman/listinfo/dmarc-discuss
FWIW, mailing lists and DMARC make a particularly noxious couple, as
almost all mailing lists will break DMARC, and thus lead to all sorts of
rejections. That very subject is the topic of the most vitriolic flame
wars on the DMARC lists.
Tho, to be honest, I had assumed that the recent changes to the From and
Reply-To headers of this mailing list were undertaken to appease strict
DMARC requirements.
Yes, Google, Yahoo and most of the rest of the Big Boys(c) have adopted
DMARC with "p=reject" (or whatever that setting is.
At the risk of perpetuating this severely off-topic thread, IMHO if
"Binarus" is able to eliminate "90% solely by checking for SPF and DKIM"
then one must question just what the rest of their anti-Spam measures
were doing?
Cheers,
-nic
--
Nic Bernstein n...@onlight.com
Onlight Inc. www.onlight.com
6525 W Bluemound Rd., Ste 24 v. 414.272.4477
Milwaukee, Wisconsin 53213-4073 f. 414.290.0335
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