offtopic: rant about thoughtless enabling DMARC checks

[Michael A. Peters]

On 2/10/19 3:46 PM, Michael A. Peters via dovecot wrote:
> On 2/10/19 3:42 PM, Noel Butler via dovecot wrote:
>> On 10/02/2019 12:49, Benny Pedersen via dovecot wrote:
>>
>>>
>>> fixing mailman will be the fail, solve it by letting opendkim and 
>>> opendmarc not reject detected maillist will be solution,
>>
>>
>> A general broad mailing list whitelist will be problematic, do work it 
>> needs to look for specific list type hidden headers,  spammers and 
>> nasties will incorporate those headers into their trash that 
>> impersonates mailing lists and voila, they pass.
> 
> However the majority of spammers do not spam with a properly configured 
> Reverse DNS - so detect the list header and skip DMARC if list headers 
> are present AND Reverse DNS matched the HELO/EHLO
> 

Also, DMARC isn't really anti-spam technology, it's anti-spoof technology.

Rather than fake mail list headers, spammers will just use domains w/o a 
DMARC policy. Much easier.