-0.105 FROM_EXCESS_BASE64 From: base64 encoded unnecessarily
-0.001 HTML_MESSAGE HTML included in message
No worry, that's expected if you send HTML emails
Checks whether your message is well formatted or not.
Your message is not signed with DKIM
You do not have a DMARC record
Your reverse DNS does not match with your sending domain.
Your message does not contain a List-Unsubscribe header