We were made aware of an issue with users attempting to send emails to Gmail.com that are being queued by the following message:
Message 169452766 to firstname.lastname@example.org delayed. Reason: 4.3.2 - Not accepting messages at this time ('421', '4.7.0 This message does not have authentication information or fails to pass', '4.7.0 authentication checks. To best protect our users from spam, the', '4.7.0 message has been blocked. Please visit', '4.7.0 https://support.google.com/mail/answer/81126#authentication for more', '4.7.0 information. l191-v6si88661wmd.224 - gsmtp') [('from', '<email@example.com>')]
4.7.0 information. e7-v6si8162728wrj.178 - gsmtp
Thanks in advance for any help/information.