I've been struggling with an email issue for the past few weeks. Two of my clients using Office 365 and Proofpoint are experiencing their receipt emails ending up in spam. We haven't made any changes to our systems, and at first, we thought it might just be due to the recipient's setup, but it's been getting worse. I've run several tests, and those were successful, and I've checked my settings with a DMARC tool, but everything seems fine. I also tried removing the smart host for Proofpoint, yet the problem persists. It's not every email—just the important ones. In my testing, only one message got flagged as spam. One strange thing was that the headers sometimes showed the email coming from an AWS IP address, which is not normal for us. I've reviewed all mailflow rules, and nothing seems off there either. I've also received headers from spam messages, and they all pass SPF, DKIM, and DMARC checks. Can anyone suggest what else I could investigate?
3 Answers
It sounds like a routing issue or something hijacking your email traffic. Since some emails go through while others don’t, it’s likely not a reputation problem. Check the return-path in the email headers to see if they match consistently. It's also worth investigating the Message-ID header; legitimate 365 emails should show certain markers, like your domain or `onmicrosoft.com`. The mention of AWS might indicate a misconfiguration.
I've seen this happen when users accidentally mark emails as spam, especially on mobile. But if multiple external recipients are affected, it seems more systemic. You might also want to check the reputation of your sending server with tools like SenderScore and MXToolbox. It's vital to ensure your IP addresses are not blacklisted.
It sounds frustrating! Just because SPF, DKIM, and DMARC pass doesn't guarantee the spam filter won't still classify your emails as junk. Have you asked your clients if their filters provide any feedback on why emails are sent to the spam folder? Also, make sure your public IP isn't blacklisted. That AWS note in the headers is odd—does the recipient's setup involve AWS in any way?
Related Questions
Can't Load PhpMyadmin On After Server Update
Redirect www to non-www in Apache Conf
How To Check If Your SSL Cert Is SHA 1
Windows TrackPad Gestures