Ensure you are also sending email from one of email accounts we have preconfigured or you have set up via our Trusted Domain process. Events in your control are the subject line and content of your HTML email. Ensure you have some text in your email and it is not all images. Don't be too salesy. Take a look at your Junk folder and this is a good example of what your email should not look like.
As long as your score is under 5, your email should not get marked as SPAM. Some email clients such as outlook will give you more leeway if there is a contact in the recipient contact list. If you have a relationship with the person you are sending email. Consider asking them to create your sending address as a contact. Another strategy for you is to send an text based email to your contact list to make sure they are not marking your sender address as a candidate for Junk email.