Slow loading times can negatively impact email campaigns in several ways. Firstly, they can increase the bounce rate, as impatient recipients may exit the email before it fully loads. Secondly, slow-loading emails can damage your brand reputation, as they reflect poorly on your business's efficiency and professionalism. Lastly, they can reduce the overall effectiveness of your campaign, as key elements like images, videos, or call-to-action buttons might not load correctly or at all.