[MlMt] From "XXX via mailmate"

["Benny Kjær Nielsen"]

On 20 Dec 2023, at 4:55, Quinn Comendant via mailmate wrote:

> On 19 Dec 2023, at 16:06, Bill Cole wrote:
>
>> Mailman modifies the "From" header of messages sent from domains which would otherwise be widely rejected […]
>> I won't try to pick apart the precise details for this list. Perhaps Benny can explain the specific rules.
>
> Mailman checks the DMARC policy published to the DNS TXT records of the domain in the "From" header of the original message. If the policy is 'p=reject' or 'p=quarantine', Mailman may modify the "From" header to use the list's email address or the server's hostname to prevent rejection due to DMARC, SPF, or DKIM checks.

Bill and Quinn are correct. The “via” is a workaround for DMARC-issues with the mailing list. This is one of those subjects where I feel like I have to start over every time I want to understand the details of what's going on ;-)

> It doesn't treat all senders the same because some people self-host their email domain and don't use DKIM or SPF.

Ironically, the mailing list server for MailMate is self-hosted (by me) and it has only been using SPF. This seems to have been a serious problem with Gmail addresses (I think many/most of them have been thrown off the list by MailMan by now).

Hopefully, the changes I've made today (on the server) means that DKIM will work going forward. That should make Google happy: https://blog.google/products/gmail/gmail-security-authentication-spam-protection/

This will NOT solve the problem which makes the use of “via” necessary for some correspondents. If I understand it correctly then a standard solution does exist now, but it's not a high priority for me to make that work: https://en.wikipedia.org/wiki/Authenticated_Received_Chain

-- 
Benny