I'm sending very simple transactional emails from SES. They always end up in my Outlook's spam folder. I've enabled DKIM signing.
The email body at the moment is very simplistic, and contains a header, two dates, and a link to sign into the app.
I've attached pics of my SES email and domain settings.
DKIM signing does not guarantee your email won't be flagged a spam. I recommend reading this AWS blog post on the subject.