I have a postfix SMTP server on Ubuntu. I have valid SPF and DKIM records, as verified by the email header my customer received.
Authentication-Results: spf=pass (sender IP is XXX.XXX.XXX.XXX) smtp.mailfrom=mydomain.com; hotmail.com; dkim=pass (signature was verified) header.d=mydomain.com;hotmail.com; dmarc=bestguesspass action=none header.from=mydomain.com;
However, the email falls into junk only in Outlook / Live.com / hotmail. The Spam Confidence Level (SCL) is 5 (spam).
X-MS-Exchange-Organization-SCL: 5 X-MS-Exchange-Organization-PCL: 2
The FAQ of SCL asks me to join 3rd party ReturnPath Certification Program to verify each email sent, but the certification program is very expensive.
Is there any alternatives to lower the SCL score? Does adding DMARC record help?
- DNS is configured correctly, including A, MX, PTR records.
- The server IP address is not on DNSRBLs (blacklist)
- Not enough sending volume to calculate Sender Score in http://www.senderscore.org
- No fake header. The mail is sent via PHP library SwiftMailer
This question is not about generic spam filter-fighting strategy; it's about Microsoft's Spam Confidence Level (SCL).