Emails are bouncing

Can this be fixed? It appears to be gmail accounts. Our domain is castletrenching.com.

Reporting-MTA: dns; bosmailout08.eigbox.net

Action: failed
Status: 5.0.0
Remote-MTA: dns; gmail-smtp-in.l.google.com
Remote-MTA: X-ip; [142.250.27.27]
X-Remote-MTA-smtp-greeting: X-str; 220 mx.google.com ESMTP vw10-20020a170907a70a00b0096ff4ade3d7si2021120ejc.500 - gsmtp
X-Remote-MTA-helo-response: X-str; 250-mx.google.com at your service, [66.96.186.8]
X-Exim-Diagnostic: X-str; SMTP error from remote mail server after end of data: 550-5.7.26 This mail is unauthenticated, which poses a security risk to the\n550-5.7.26 sender and Gmail users, and has been blocked. The sender must\n550-5.7.26 authenticate with at least one of SPF or DKIM. For this message,\n550-5.7.26 DKIM checks did not pass and SPF check for [castletrenching.com] did\n550-5.7.26 not pass with ip: [66.96.186.8]. The sender should visit\n550-5.7.26  https://support.google.com/mail/answer/81126#authentication for\n550 5.7.26 instructions on setting up authentication. vw10-20020a170907a70a00b0096ff4ade3d7si2021120ejc.500 - gsmtp
Diagnostic-Code: smtp; 550-5.7.26 This mail is unauthenticated, which poses a security risk to the
 550-5.7.26 sender and Gmail users, and has been blocked. The sender must
 550-5.7.26 authenticate with at least one of SPF or DKIM. For this message,
 550-5.7.26 DKIM checks did not pass and SPF check for [castletrenching.com] did
 550-5.7.26 not pass with ip: [66.96.186.8]. The sender should visit
 550-5.7.26  https://support.google.com/mail/answer/81126#authentication for
 550 5.7.26 instructions on setting up authentication. vw10-20020a170907a70a00b0096ff4ade3d7si2021120ejc.500 - gsmtp