Why is my email marked or rejected as SPAM?

Some of the detail below IS TECHNICAL, but then we are trying to solve a technical issue. 

The link below provides a short overview and contains a short video with a brief explanation of what might be going wrong and what to avoid.

blog.gimm.io/email-signatures-and-spam-filter-problems/

Test the Spammyness of your Emails

1. At Mail-tester.com you can use a free tool for analyzing specific emails and their content.
2. Spamcheck is another email testing option
3. Check your Email Deviverability using MXToolbox.com

You might be asked to paste message headers into a webpage

What are message Headers?

Check out how to "View internet message headers in Outlook"

if you are not using Outlook, then try a similar Google search for whatever mail program you are using on your computer of device.