DMARC/SPF configuration error

Mailchimp does not support SPF as it uses its own domain in the bounce address. Their domain authentication verification tool requires including Mailchimp, though. Mailchimp always fails DMARC's SPF alignment test because the Return-Path path doesn’t match the From address. MailChimp doesn't support custom Return-Path (even though Mandrill, which is owned by Mailchimp, does). This makes it impossible to be 100% SPF-compliant under DMARC rules with Mailchimp.

I'm not 100% sure, but I'd guess that if the domains for return-path and from header have to match, you would need to have a CNAME DNS record in your own domain pointing at MC, so that the domains could match, something like:

mc CNAME mail125.suw11.mcdlv.net

Then your return path might become <bounce-mc.us17_88978185.265251-recipient=patentbots.com@mc.mydomain.com>.

I don't know if a subdomain match like this is sufficient, i.e. whether DMARC considers mc.mydomain.com and mydomain.com to be sufficiently aligned.

I can see the management of this being a little tricky if you have lots of domains.