mailserver: Enable DMARC reporting

[mweinelt]

When someone sends us mail and their domain has rua= configured in their DMARC record we send back daily deliveriability summaries.

[jfly]

Thanks! I see you're the one who added DMARC support to SNM, haha.

I sure would like for SNM to help complete email noobs to get this stuff right. I read through the whole setup guide and it never told me this would be a good idea to enable. I'd like to try to contribute something back to upstream here. What do you think would be appopriate?

1. Enable dmarcReporting by default.
2. Add a note to the SNM setup guide advising people to turn this on.

[mweinelt]

I think this should be opt-in and therefore go into documentation.

[jfly]

I can send in a docs PR. Can you help me understand when it would make sense for people not to turn this on? Is it a privacy thing? (avoid responding to people you don't trust?)

[mweinelt]

Not sure what a good metric is when to enable this. It basically sends out automated reports to domain owners about deliverability results.

It is not strictly required or helpful for your personal mail setup, it is more about being a good citizen in the mail ecosystem.

[jfly]

It is not strictly required or helpful for your personal mail setup, it is more about being a good citizen in the mail ecosystem.

I've suggested this here: https://gitlab.com/simple-nixos-mailserver/nixos-mailserver/-/merge_requests/377. If this had existed when I started working on the nixos mailserver, I would have followed the advice and enabled DMARC reporting.

[mweinelt]

https://gitlab.com/simple-nixos-mailserver/nixos-mailserver/-/merge_requests/340 would be good to have before we enable this.