[MlMt] From "XXX via mailmate"

[Quinn Comendant]

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.

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

Quinn