If Postmark's DMARC digest flags SPF failures on your Mailchimp mail while your SPF record looks correct, stop editing DNS: it is expected. Mailchimp sends with its own bounce domain and offers no custom Return-Path, so SPF alignment fails by design under DMARC. The only full fix is DKIM alignment or a sender that supports a custom Return-Path. Treat digest SPF failures on Mailchimp-sourced mail as informational, not as a misconfiguration to chase.

Context: Stack Overflow #50469686 (answer score 17): A user's DNS looks correct, with Mailchimp's servers in the SPF record, yet Postmark's weekly DMARC digest reports SPF failures on Mailchimp-sent mail. The answer explains this is not a DNS mistake: Mailchimp uses its own domain in the bounce address and does not support a custom Return-Path, so its mail always fails DMARC's SPF alignment test even when the SPF record is right. No DNS change fixes it.