Hey @david-z. Welcome!
While @karstenkoehler is right that the ideas section may see more support from HubSpot, these breaks, gaps, or whatever you want to call them, appearing in Outlook is pretty well documented in the broader email marketing community. It’s particularly problematic among older versions.
This is because those older versions of Outlook relied on Word to render HTML - which leads to all kinds of problems with modern programming/coding, as well as drag-and-drop editors.
Sometimes it’s a matter of trial and error, but some common tactics include these from Litmus and Email on Acid.
- Litmus: Outlook Email Rendering Issues and How to Solve Them - Litmus
- Email on acid: How to Code HTML Emails that Look Good in Outlook.com
Personally, I recommend trying some different font sizes. Sounds too simple, but I’ve found success by changing font sizes, heights, padding, etc., to even numbers. So if you’re using 15px or something similar, try using 14px or 16px.
Hopefully this helps! If it does, please mark it as a solution.
Good luck and Godspeed!