Why does formatting break when Outlook users forward my email?

We noticed when subscribers forward our email in Outlook that the forwarded copy pretty much triples or quadruples the white space between headers, text, and paragpaphs. I would like to understand if this is typical for forwarded email (or at least typical for Outlook) and if there is something I might be able to do with formatting that help keep it standard across the different way people engage with our emails.