The task of developing Outlook HTML emails can be frustrating (to say the least). This should help! Get advice for troubleshooting Outlook issues.
https://www.emailonacid.com/blog/article/email-development/how-to-code-emails-for-outlook-2016/
* getting rid of lines in Outlook emails * ghost columns * Holly Bourneville also recommends * Grab more code snippets * Can I Email now indicates * alternative solution for GIFs in Outlook * email spacing techniques * tips for margins and HTML email padding * fonts in email marketing * Outlook and font stacks * get code snippets * CSS background images with Outlook.com and Outlook 365 * Vector Markup L * a * nguage (VML) * Microsoft Office styles (MSO styles * fluid hybrid design for responsive emails * use ghost tables to fix Outlook alignment * run unlimited tests