On Apr 10, 2014, at 9:21 AM, Al Iverson <[email protected]> wrote:

> On Thu, Apr 10, 2014 at 1:04 AM, Roland Turner
> <[email protected]> wrote:
> 
>> I am going to assume that Yahoo!'s email people haven't lost their minds and
>> - despite the failure to give a heads up - actually did carefully assess the
>> impact of the change before making it<snip>
> <snip>
> Here's another great example of a commercial discussion list provider
> responded quickly to implement product changes that allow Yahoo users
> to continue to participate in the lists they host:
> http://onlinegroups.net/blog/2014/04/10/yahoo-dmarc-better-mailing-list-manager/
> 
> I bet we'll see lots more of this in the near future.

And it's a welcome improvement over the status quo.

Starting in January, my posts to one mailing list began to be refused because I 
publish a DMARC p=reject policy. I admit that I recklessly deployed DMARC, 
learning empirically exactly what the costs and benefits are. 

BENEFITS:

        The bounce messages I used to regularly receive from purported 
@tnpi.net senders ceased, primarily because 123.com enforces DMARC. The abusers 
of my domain name are mostly bots in China and their email attempts are 
rejected before stupid mail servers accept and then bounce them to me 
(backscatter).

COSTS:

        One year later, I can't send emails to exactly two lists via that 
domain (one because of a technical block, the other out of respect for the list 
admins request). That's a cost I pay to prevent the abuse of my domain and the 
annoyance of backscatter in my inbox. 

        The backscatter I used to get is now pushed onto list admins who get 
the bounces when they attempt to deliver a message whose DKIM signature they 
broke. While I'm not particularly delighted to foist that upon them (I too have 
been managing lists for *decades*), it seems a perfectly reasonable trade off. 
Domain owners shouldn't be required to tolerate abuse because recalcitrant list 
owners refuse to *slightly* change how their lists operate.

----------

In spite of the assertions by certain persons that DMARC is unsuitable for 
domains with human users, I have deployed it for a couple other domains which 
had persistent email abuse issues. Their abuse issues aren't phishing but 
rather identity sullying by politically motivated attackers who disagree with 
their stance on "way too liberal" policy issues. Publishing DMARC records for 
their domain hasn't stopped the attacks but it did slam the door shut on the 
email attack vector.

Hundreds or thousands of empirical examples like mine would never sway the John 
Levine's to admit that DMARC is workable and even beneficial to small domain 
owners. But Yahoo! just did that for us. This move was likely motivated by the 
benefits Yahoo accrues but the changes they foist onto list admins also makes 
DMARC far less costly for Domain Owners with human users.

Yahoo also paved the way for Google and Microsoft to deploy p=reject policies. 
Recalcitrant list operators who take the "Stop using Yahoo" tack will be 
wearing egg facials when that happens.

Matt


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