My emails going to spam folder for hotmail or outlook

My emails (not spam mails) are going into the spam folder for my customers using hotmail. Gmail and Yahoo users are receiving the emails in their inbox. can you please solve this problem. I read few articles but coudnt find any solution to it.

I am testing it by sending a simple text email no pictures nothing at all still it is filtering my emails as spam.

Please help I am really loosing time and clients due to this.

Thanks