The recommended size for an HTML email signature can vary depending on the specific platform or email client you are using.
However, as a general rule of thumb, you should aim for an email signature that is no more than 600 pixels wide and 100 to 200 pixels tall. This will ensure that your signature is easy to read and does not take up too much space in the recipient’s email inbox.
It’s also a good idea to use a responsive design for your email signature, so that it looks good on a variety of devices with different screen sizes. This can be achieved by using a combination of HTML and CSS to create a flexible layout that adjusts to the available space.
Finally, be sure to use clear, legible fonts and avoid using too many different font sizes and styles, as this can make your email signature difficult to read.