Images can look blurry or pixelated in an email for several reasons:

• Image resolution: If the image has a low resolution, it will appear blurry or pixelated when scaled up or viewed on high-resolution screens. To avoid this, use high-quality images with a resolution of at least 72 pixels per inch (ppi) for web images and 300 ppi for print images.
  
• Image compression: Images that are compressed too much can lose their quality and appear blurry or pixelated. To avoid this, use the appropriate image compression settings for the web and optimize images for the web using tools such as Adobe Photoshop or online image compressors.
  
• Scaling: If the image is scaled up or down too much, it can appear blurry or pixelated. To avoid this, use images that are the appropriate size for the email or use tools such as Adobe Photoshop or GIMP to resize the image without losing quality.
  
• Device resolution: If the recipient’s device has a low screen resolution, the image may appear blurry or pixelated. To avoid this, use images that are optimized for a wide range of devices and screen sizes.
  
• Email client: Some email clients may automatically compress images or display them at a lower resolution, which can cause them to appear blurry or pixelated. To avoid this, test the email on different email clients to ensure that the images appear as intended.

To ensure that your images appear clear and sharp in an email, use high-quality images, optimize them for the web, and test the email on different devices and email clients.