Why are my Mailchimp emails bouncing with an “SPF/DKIM failed” warning?

Mailchimp bounces occur when your sending domain’s DNS is not verified, meaning you haven’t added Mailchimp’s required DKIM (CNAME) and SPF (TXT) authentication records.

“The usual culprit is a sending domain that was never fully verified with Mailchimp’s required authentication records. I’ll get it verified and bouncing stopped within 24 hours for $99.”
— Jeff Bollettino, Managing Director, Ignite Conversions