Here is a raw message received in Gmail and was marked spam for troubleshooting: Testing mail Reachability.eml
Possible causes:
- Sender IP is blacklisted – Emails are sent from Zoho mailbox since it was the only free services that allows setting up DKIM. The Zoho support repeatedly claims that their IP reputation is good.
- Domain name has bad reputation – A different domain has never been used hence unable to check this out.
- Google defaults mails from unusual domains to spam – If this is the case nothing can be done about it other than asking all receivers to “Report not Spam”
