Hello, This is my second time of posting about this issue, which involves messages sent from our MS 365 Tenant being rejected by Google's mail servers.
Around the beginning of April, several of our users started to get messages bouncing back, when sending messages to Google-hosted domains. The error received each time was as follows: Error: 550 5.7.350 Remote server returned message detected as spam -> 550 5.7.1 [2a01:111:f403:261b::701 19] Gmail has detected that this message;is likely suspicious due to the very low reputation of the sending;domain. To best protect our users from spam, the message has been;blocked. For more information, go to; https://support.google.com/mail/answer/188131 af79cd13be357-792cf65c157si1015450885a.765 - gsmtp Message rejected by: mx.google.com The same would happen when sending to any Gmail account. The first thing I checked was the SPF, DKIM and DMARC records, but found they were all correct. So, I contacted Microsoft 365 Support for assistance. They looked at the message, immediately blamed Google, and told me to speak to them. Unfortunately, there is no one to speak to at Google, unless your domain is hosted with them. So I filled out several of Google's email case reports, none of which have been acted upon. Microsoft have tripled checked the SPF, DKIM and DMARC records and have confirmed they are all correct and are baffled as to why it is not working. Each time I am told that it is a 'Google Problem' and we need to get out domain whitelisted by them. We are now in the position whereby mails sent to these domains are either rejected outright by Google's servers or end up in users' Spam folders. I registered with Google Postmaster Tools a few weeks ago and finally got some analysis a few days ago, as follows: SPF and DKIM authentication Needs work - Set up both SPF and DKIM authentication. SPF prevents spammers from sending unauthorised messages that appear to be from your domain. Receiving servers use DKIM to verify that the domain owner actually sent the message. From: header alignment Needs work - Ensure that the From: header aligns with either SPF or DKIM For direct mail, the domain in the sender's From: header must be aligned with either the SPF domain or the DKIM domain. This is required to pass DMARC alignment. DMARC authentication Compliant Encryption Compliant User-reported spam rate Compliant DNS records Compliant The above makes no sense to me, as it is suggested there is an issue with the SPF and DKIM records and that the From header, yet all are correct. Everything else on the Google Postmaster Tools passes. Has anyone seen this before, and if so, is there a solution, as neither Microsoft, nor Google will assist? Any advice would be much appreciated. Thanks, Simon
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