Some of our full service email users reported an issue with delivering emails to Gmail users with the error message below. As indicated in the error, the issue is that the sending domain's SPF and DKIM are not set up.

Error Type: SMTP
Remote server (142.250.102.26) issued an error.
Remote server replied: 550-5.7.26 This mail is unauthenticated, which poses a security
550-5.7.26 risk to the 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 [xxxxxx.com] did not
550-5.7.26 pass with ip: [162.216.242.37]. 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.
o5-20020a170906774500b008c580ab8d9esi8642798ejn.69 - gsmtp

We have a tutorial for full service email configuration that explains what SPF and DKIM records to set up and how. Users with SMTP outbound relay service can refer to this tutorial for SPF and DKIM setups.

If you have any questions or concerns, open a support ticket and we'd be glad to assist you.