I have tried to send emails from my outlook mail ID and it ends up going straight to spam all the time. This is not a problem that is happening only to me. My friends are facing the same problem. I used Mxtool to find the problem. It says the reverse DNS lookup is unable to take place. And it lists out a bunch of problems with my email. I know for a fact that if the reverse DNS lookup isn't happening then the email will go straight to spam.
I ran an online tool to find the problem. I have attached an image of the report.