- Broken Links: Links that do not work can frustrate users and lead to missed opportunities for conversions. - Unoptimized Images: Images that are too large or not properly formatted can slow down load times and may not display correctly. - Inconsistent Rendering: Emails may look different on various email clients and devices if not coded properly. - Unreadable Text: Poor use of fonts, colors, and layouts can make text difficult to read. - Accessibility Issues: Emails that are not accessible can alienate users with disabilities.