Re: Amavis and OpenDMARC

On 12/11/2023 13:03, Nick Tait wrote:

> On 12/11/23 15:10, Noel Butler wrote:
> 
>> DMARC (thus OpenDMARC) makes its decision based on the senders DMARC 
>> fo policy -
>> 
>> if policy uses fo=0  then yes, both SPF and DKIM must exist, and both 
>> must pass.
>> 
>> if policy uses fo=1  then no, as a minimum _either_ SPF or DKIM must 
>> exist, and pass, so DMARC will work with only SPF or only DKIM, it 
>> will also work with both, which has the advantage that only one of 
>> these must pass, eg: SPF passes but DKIM fails, DMARC usinng fo=1 will 
>> pass.
>> 
>> I recommend fo=1 for general use but fo=0 for critical areas, like 
>> govts, legal and finance sectors, or those who deal with them on a 
>> very regular basis, in which case they wouldn't be authorised to use 
>> there govt/corp email for private use so if ill-configured mailing 
>> lists for example rejected them, then that's acceptable collateral 
>> damage.
> 
> Hi Noel.
> 
> My understanding of the "fo" option is that it is only used for 
> reporting. i.e. It doesn't control whether the received email is 
> accepted or not, which is always based on _either_ SPF or DKIM checks 
> passing.
> 
> From RFC 7489:
> 
> fo:  Failure reporting options (plain-text; OPTIONAL; default is "0")
> Provides requested options for generation of failure reports.
> Report generators MAY choose to adhere to the requested options.
> This tag's content MUST be ignored if a "ruf" tag (below) is not
> also specified...
> 
> Nick.

Ahhh you're right, my very bad, I was confusing r/s ...

/slap shouldnt do email first thing early Sunday morning after being up 
till 3am watching Cricket :)

-- 
Regards,
Noel Butler

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