Microsoft Exchange blocking SES

Hi, I've been using Simple Email Service for some months without issues. I recently noticed that emails sent to accounts of organizations using Office365 end up in the junk folder. I checked the email headers of such emails, the problem is that the SCL check returns a value of 5, getting the email marked as spam. Every other spam test seems to be ok.

SPF, DKIM and DMARC are properly set up: the authentication result in the rejected mails header states pass for both SPF and DKIM (anyway, just a month ago everything was working properly and I did not change configurations). Using an online tool like mail-tester.com everything turns out to be correct. I use SES with a very low amount of traffic, there is no way that contents that are really spam were sent from my domains. The account is not in the sandbox, bounce rates and complaints are exactly 0%.

Why is this happening? Is there something I can do?