My emails keep returning with SMTP errors. How do I address this?

When I send a group email, several come back with SMTP errors. How do I fix this?

Here's what I receive:

Action: failed
Final-Recipient: rfc822; [recipient email address]
Status: 5.0.0
Remote-MTA: dns; gmail-smtp-in.l.google.com
Remote-MTA: X-ip; [172.253.122.27]
X-Remote-MTA-smtp-greeting: X-str; 220 mx.google.com ESMTP c129-20020ae9ed87000000b00742709be80asi587682qkg.87 - gsmtp
X-Remote-MTA-helo-response: X-str; 250-mx.google.com at your service, [66.96.188.3]
X-Exim-Diagnostic: X-str; SMTP error from remote mail server after end of data: 550-5.7.26 This message does not pass authentication checks (SPF and DKIM both\n550-5.7.26 do not pass). SPF check for [describeeditorial.com] does not pass\n550-5.7.26 with ip: [66.96.188.3].To best protect our users from spam, the\n550-5.7.26 message has been blocked. Please visit\n550-5.7.26  https://support.google.com/mail/answer/81126#authentication for more\n550 5.7.26 information. c129-20020ae9ed87000000b00742709be80asi587682qkg.87 - gsmtp
Diagnostic-Code: smtp; 550-5.7.26 This message does not pass authentication checks (SPF and DKIM both
550-5.7.26 do not pass). SPF check for [describeeditorial.com] does not pass
550-5.7.26 with ip: [66.96.188.3].To best protect our users from spam, the
550-5.7.26 message has been blocked. Please visit
550-5.7.26  https://support.google.com/mail/answer/81126#authentication for more
550 5.7.26 information. c129-20020ae9ed87000000b00742709be80asi587682qkg.87 - gsmtp