Gmail (and other similarly configured email providers) will no longer be accepting messages where the From domain is a Gmail address and the message originates from a non-approved Gmail mail domain server/service (which includes email marketing services like ContentMX). This is a security measure they have implemented to help reduce potential address spoofing of their mail domains.
What this means: You are not able to send email campaigns with a Gmail address as your From address when sending to a domain that checks DMARC before accepting mail.
What you should do: You will need to change the From address you use in emails to a non-Gmail address. We recommend using one at your own mail domain or one you control. You can then set the Reply-To address of the email campaign to be the original Gmail address that previously was used in the From field.
Are messages previously sent before this change lost? Yes, any email with this bounce condition is discarded and considered Blocked. You will need to adjust your From address field settings, and then try resending.
How do we know when this is happening? Gmail has recently decided to embrace DMARC more explicitly, like Yahoo and AOL. Accordingly the system will start generating bounce messages with this error that are visible to our support team when checking the server logs:
“550 5.7.1 Unauthenticated email from [DOMAIN] is not accepted due to domain’s DMARC policy. Please contact administrator of [DOMAIN] domain if this was a legitimate mail. Please visit https://support.google.com/mail/answer/2451690 to learn about DMARC initiative.”