>people rarely read my emails if it doesn't fit in their screen

I think this is the case unless the problem is very relevant to what you are working on at the moment. Normally what I would do, if I were writing an email to explain a problem, is create that explanation in depth on a wiki or other knowledge repository somewhere. Write the email referencing the url of this wiki, and explain the main points in the email.

This is as a general rule if I am explaining something important for tech team to know, if I am explaining something that is important for product owner to know I write it in as verbose an email as is required to explain everything. That's up to the product owner to follow. Generally after receiving an email like this they will want a meeting where I can explain in person and draw stuff on the whiteboard.