Hi,
This is probably due to missing authentication in your emails or you are trying to send with phpmail.
Couple of things you can do:
- You should get a third party SMTP.
This is how it’s set up: https://mautic.com/help/email-transport/ - Here is another forum where we are discussing email sending in general:
What tool to use to send millions of e-mails per month - To authenticate your emails, you need to set up DKIM, SPF and dMARC.
https://www.smartertools.com/blog/2019/04/09-understanding-spf-dkim-dmarc
One more thing. If you send an email from yourself to yourself via php, than you’ll probably get the spoofing message. Sender and recipient should be always different.
Good luck!