This is a new problem, only started happening about two weeks ago. We autoforward emails from our domain mailboxes to groups of people, some of whom have Gmail addresses. Autoforwarding to email addresses other than Gmail always work.
Forwarding to Gmail addresses works some of the time, but about a third of the emails are rejected by Google mail as having insufficient authentication. This can happen with two emails sent by the same person within minutes of each other - one will be autoforwarded successfully to all addresses, the next will not be autoforwarded to Gmail addresses. I have checked with our hosting provider and the emails are definitely being forwarded on, and we have all the appropriate SPF, DKIM and DMARC DNS records in place.
We depend on this autoforwarding to work consistently for communication within our community organisation, and the recent intermittent failures are driving us crazy. Do I have to tell all the people who have Gmail accounts to use another mail service?