A responsive email is an email that is designed and coded to adapt and display properly across different devices and screen sizes, including desktops, laptops, tablets, and smartphones. Since email clients and devices have varying capabilities and display dimensions, creating responsive emails ensures that the content and layout of the email adjust dynamically to provide an optimal viewing experience for recipients.

To create a responsive email, consider the following steps:

1. Use a responsive email template: Start with a pre-designed responsive email template or framework. This provides a solid foundation and saves time compared to building an email from scratch.
   
2. Structure the email with tables: Use HTML tables to structure the email layout. Tables allow for more control over the placement and alignment of content in different email clients.
   
3. Implement media queries: Media queries are CSS code snippets that apply specific styles based on the device’s screen size. By defining different styles for different screen widths, you can adjust the layout and formatting of the email accordingly.
   
4. Optimize images: Ensure that images in the email are appropriately sized and optimized for faster loading. Use responsive image techniques, such as setting the maximum width to 100% to prevent image overflow on smaller screens.
   
5. Simplify the design: Keep the design clean and uncluttered. Minimize the use of large images, excessive text, and complex formatting that may not translate well on smaller screens.
   
6. Use scalable fonts and buttons: Choose fonts that are legible across various devices and adjust their size using relative units like percentages or ems. Make buttons large enough to be easily tapped on touchscreens.
   
7. Test across devices and email clients: Test the responsive email on different devices, email clients, and operating systems to ensure consistent rendering. Use testing tools or send test emails to different accounts and check how the email appears in various environments.
   
8. Monitor analytics and user feedback: Analyse email metrics like open rates, click-through rates, and user feedback to evaluate the effectiveness of your responsive emails. Make adjustments based on the insights gained to improve future campaigns.

Remember that creating responsive emails requires knowledge of HTML, CSS, and email design best practices. Alternatively, you can use email marketing tools or services that offer drag-and-drop builders with responsive templates, making the process more accessible to users without coding expertise.