Adding a watermark to your email can be done in various ways:
1. Email Builders: Most email marketing platforms like Mailchimp or Constant Contact allow you to upload background images. Insert your watermark as a background image. 2. HTML and CSS: If you are coding your email, use CSS to set the watermark as a background image with the `background-image` property. 3. Email Templates: Modify existing templates to include your watermark.