[dmarc-discuss] options on multiple from

Franck Martin fmartin at linkedin.com
Wed Jul 17 11:13:58 PDT 2013


On Jul 17, 2013, at 10:32 AM, John Levine <johnl at taugh.com> wrote:

> It seems to me that there is a fairly short list of ways that DMARC can deal
> with addresses with more than one address on the From line:
> 
> a) exclude them, anything with multiple addresses fails
> b) if the two addresses are in the same domain, do the usual thing, otherwise fail
> c) evaluate separately, take the strictest result
> d) evaluate seaparetly, take the loosest result
> 
> Fail would probably mean to apply the failure rule for each domain so a) is in
> practice pretty close to c)
> 
> I think it is reasonable to say that if you want to use DMARC, don't
> use multiple addresses, since it's not a feature that is well
> supported anywhere.
> 

I'm not sure what fail means here?
1) bounce the email
2) dmarc test failed, so what policy to apply?

If fail means bounce the email, then it contradicts earlier RFCs where multiple emails in From is ok (and even none at all in a recent RFC). So it is hard to be normative here when you contradict previous RFCs. You can only provide advice to receivers on how to handle such emails (aka BCP).

I encourage people to check their incoming mail streams and identify emails with multiple addresses in From: and check which ones are valid constructs or more caused by a buggy (or lazy as Murray said) MTA. 


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