The banner says: "This message seems dangerous. Many people marked similar messages as phishing scams, so this might contain unsafe content. Avoid clicking links, downloading attachments, or replying with personal information."

The app in question is a monitoring service, and the emails it sends are monitoring alerts. The app does not send "Hey, how are you getting on?" style lifecycle emails. The emails don't have tracking pixels, no links or pictures pointing to 3rd party domains. They have no attachments.

I've tried a number of things to fix this:

* checked and double checked my website and my emails don't contain any unexpected content like malware

* verified DKIM, SPF, DMARC records. Gmail itself shows all three as valid

* added List-Unsubscribe header to the emails

* checked the bounce and complaint rates, both are low around or below 0.1%

* reduced the number of http links in the emails

And the warnings are still showing up. I'm out of ideas on how to troubleshoot this. Has anyone else run into this problem, any tips? Thanks!

Edit: example of the Gmail warning: https://i.imgur.com/XG41FJ0.png