How do I troubleshoot issues with email formatting or layout?

Check spelling of your HTML tags and attributes
Make sure HTML tags are properly closed and nested
Validate HTML with a validator like W3C
Verify that your HTML is supported in the Email client you are targeting
Check any custom styling and attributes; make sure you are using inline styling for your style attribute
Confirm that any external images used are pointing at a valid, secure location
Test against multiple Email clients such as desktop, mobile, and web clients
Ensure your HTML contains proper line breaks to stop unintended line framing and block elements collapsing