From version 3.2.2 onwards phpList has a method to define and use a logo in campaigns. The logo will be included in the campaign content, and display in the message even if subscribers block access to images.
This functionality requires PHP5.4 or up.
To set the logo, you can upload an image to the settings for Logo. You can upload a PNG or JPG image with as best quality as you have.
Once you have uploaded your logo, you can use it in templates and the content of your campaigns. You can use it as the “src” of the image.
<img src="[LOGO]" width="X" height="Y" alt="*" />
This will include the Logo as uploaded.
<img src="[LOGO:300]" alt="*" />
This will include the logo with the largest side being 300 pixels.