Microsoft deliverability

Hi David,

Thank you for your answer. 

It's kind of a mystery tbh. We use the drag-and-drop editor (will double-check for 'if mso' thanks for that tip) and our emails are quite light on the image/text front, we use benchmarks for ratios, fingerprinting...etc, so we are running dry on what else can it be.
Complaints used to come as SRDs (Microsoft's most accurate way to measure complaints) but all of a sudden they just changed to "Overall Complaint Rate". The interesting bit is that we are currently warming a brand new IP with a minimum rate (still early days on the warm-up) this is being done with transactional emails and highly engaged users, but still, the complaint rate is coming back as 1 in every 2 emails are counted as a complaint, this is statistically unlikely and never seen it before.

We also have customers mentioning to us that they have marked our email s as not spam several times and Microsoft keeps delivering to the spam folder. I have been running this test myself for the last 6 months and I have marked the at least 50 times as not spam and they still land on spam. 

Are there anyonther tips you can share on how could this happen or if there is any documentation that Microsoft shares on how to increase deliverability on the more technical deeper side (not the typical deliverability rules as engaged, subject lines, etc etc) 

In advance thanks for your help