==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release):  1.4.0 MARIADB edition
- Deployed with iRedMail Easy or the downloadable installer? installer
- Linux/BSD distribution name and version: Ubuntu server 20.4
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx):Nginx
- Manage mail accounts with iRedAdmin-Pro? no
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

Hi All

So I have a strange problem.

I have Iredmail set up and working perfectly.  I have correctly configured DNS records – MX, SPF, DKIM and DMARC are all good.  If I send a test email to https://www.mail-tester.com I get a 10/10.  I can send emails to Gmail no problem. My public IP does not have any reputation issues and is not on any blacklists.

But – If I send emails to any user on Microsoft 365, they almost always end up in the Junk Mail folder.  I have looked at the headers and according to MS, they have a Spam Confidence Level or either 5 or 6, but there is nothing to explain WHY they have an SCL this high.  This is a big problem from me as many of my users will want to send emails to MS 365 addresses.  Can anyone suggest a solution?

Thanks in advance.