Question about DMARC

[Wesley Peng]

Greetings,

When mail is relayed through mailing list, why the DMARC policy is 
possible to reject?

For example, I sent mail from x...@mail.ru to y...@googlegroups.com

Since mail.ru has the strictest DMARC policy, the recepients may choose 
to reject this mail which is relayed by googlegroups, the reason is due 
to DKIM or SPF fails.

So mailing list makes DKIM or SPF failed?

Thank you for your helps.

Regards.