Kit (Formerly ConvertKit) Templates Are Limited: How to Hack the Design Constraints

You have likely heard the common advice in the email marketing world: “Plain text emails convert better.” This is the philosophy that Kit – formerly known as ConvertKit – was built upon. The platform prioritizes deliverability and a direct, personal connection over flashy design. For many mission-driven organizations and creators, this is a feature, not a bug. It strips away the corporate veneer and allows you to speak directly to your donors or audience.

However, there is a distinct difference between “simple” and “unbranded.”

The reality for many of our clients at our nonprofit marketing agency is that visual identity matters. When you are asking for donations or trying to establish authority in a crowded space, your emails need to look professional. They need to match the aesthetic of your website and your social media presence. The default templates provided by Kit often fall short in this regard. They are rigid, difficult to customize without code, and can leave your brand looking generic.

If you have ever tried to force a multi-column layout or a custom font into a Kit broadcast only to have it break on mobile, you know this frustration well.

This guide is a technical deep dive into how you can bypass these limitations. We are going to look at how to “hack” the design constraints of Kit using standard web development practices, specifically tailored for the email environment. We will cover how to inject custom CSS, build robust HTML shells, and even use AI to generate the code you need if you are not a developer.

The Core Problem: Web HTML vs. Email HTML

Before we start pasting code, it is critical to understand why Kit’s editor feels so limited compared to a website builder.

Web browsers are incredibly sophisticated engines that follow modern standards. When we build custom websites for our clients, we use advanced CSS grids, flexbox, and JavaScript to create fluid, responsive layouts. Email clients – like Outlook, Gmail, and Apple Mail – are not web browsers. They are much older, and their rendering engines are inconsistent.

Outlook, for instance, uses the Word rendering engine, which has barely changed in two decades. It does not understand modern CSS. Gmail strips out entire blocks of code to prevent security risks. This is why email developers still use 1990s-style HTML tables for layout instead of <div> tags.

Kit’s visual editor is restricted because it is trying to protect you from yourself. It limits your design options to ensure that your email actually lands in the inbox and looks readable, whether your subscriber is on an iPhone or a desktop computer running Windows 98.

But we can push these boundaries safely if we know the rules.

The Hybrid Approach: Shells and Snippets

The most effective way to customize Kit without breaking deliverability is a “Hybrid” approach. We do not want to hand-code every single email from scratch – that defeats the purpose of using a tool like Kit. Instead, we want to create a reusable system.

This system has two parts:

1. The HTML Shell: A master template that defines the outer edges of your email (header, footer, background colors, and global fonts).
2. CSS Snippets: Little blocks of code you can drop into the standard visual editor to style specific elements like buttons, testimonials, or call-out boxes.

This allows you to maintain the ease of the drag-and-drop editor for your daily content while keeping the strict brand control of a custom-coded template.

Phase 1: The HTML Shell (The Container)

The shell is where you define your brand’s global constraints. In Kit, you can create a custom HTML template by going to Send > Email Templates > New Email Template > HTML.

Do not be intimidated by the blank screen. You are essentially building a container. The most important part of this container is the “content placeholder.” This is a special tag that tells Kit, “Put the visual editor content right here.”

Here is a robust, responsive shell structure that fixes many of the common spacing and font issues in the default templates. This template forces a centered layout and sets a background color distinct from the content area – a simple change that instantly elevates the design.

The Code Structure

We are going to use a table-based structure for maximum compatibility.

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <style>
    /* Client-specific resets */
    body, table, td, a { -webkit-text-size-adjust: 100%; -ms-text-size-adjust: 100%; }
    table, td { mso-table-lspace: 0pt; mso-table-rspace: 0pt; }
    img { -ms-interpolation-mode: bicubic; border: 0; height: auto; line-height: 100%; outline: none; text-decoration: none; }
    
    /* Global Styles */
    body {
      background-color: #f4f4f4; /* Outer Background */
      margin: 0;
      padding: 0;
      width: 100% !important;
      font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
    }
    
    .wrapper {
      width: 100%;
      table-layout: fixed;
      background-color: #f4f4f4;
      padding-bottom: 40px;
    }
    
    .main-content {
      background-color: #ffffff; /* Inner Content Background */
      margin: 0 auto;
      max-width: 600px;
      width: 100%;
      border-radius: 8px; /* Rounded corners for the card look */
      overflow: hidden; /* Ensures content stays inside rounded corners */
      box-shadow: 0 4px 6px rgba(0,0,0,0.05); /* Subtle drop shadow */
    }
    
    .content-padding {
      padding: 40px 30px;
    }

    /* Mobile Styles */
    @media screen and (max-width: 600px) {
      .content-padding {
        padding: 20px 15px !important;
      }
      .main-content {
        width: 100% !important;
        border-radius: 0 !important;
      }
    }
  </style>
</head>
<body>
  <div class="wrapper">
    <table role="presentation" border="0" cellpadding="0" cellspacing="0" width="100%">
      <tr>
        <td align="center" style="padding-top: 40px;">
          <table role="presentation" border="0" cellpadding="0" cellspacing="0" width="100%" style="max-width: 600px;">
            <tr>
              <td align="center" style="padding-bottom: 20px;">
                <img src="YOUR_LOGO_URL_HERE" alt="Brand Logo" width="150" style="width: 150px; display: block;">
              </td>
            </tr>
          </table>
          <table role="presentation" class="main-content" border="0" cellpadding="0" cellspacing="0" width="100%">
            <tr>
              <td class="content-padding">
                <div class="message-content">
                  {{ message_content }} 
                  </div>
              </td>
            </tr>
          </table>
          <table role="presentation" border="0" cellpadding="0" cellspacing="0" width="100%" style="max-width: 600px;">
            <tr>
              <td align="center" style="padding-top: 20px; color: #888888; font-size: 12px;">
                <p>{{ address }}</p>
                <p><a href="{{ unsubscribe_url }}" style="color: #888888; text-decoration: underline;">Unsubscribe</a></p>
              </td>
            </tr>
          </table>
          </td>
      </tr>
    </table>
  </div>
</body>
</html>

This shell does something the default “Modern” template in Kit does not do well: it creates a distinct “card” effect. By separating the background color (#f4f4f4) from the content background (#ffffff), you instantly make the email look more polished and easier to read.

Using AI to Generate Custom Shells

You might not want the exact style above. This is where you can leverage AI tools. Since you are looking to save time on marketing automations, you can use a prompt like this in ChatGPT or Claude to generate a shell that matches your brand colors.

Prompt for AI:

“Write a custom HTML email template for ConvertKit. It needs to include the {{ message_content }} variable. Use a table-based structure for Outlook compatibility. The design should have a dark blue background (#003366) for the outside, and a white container for the text. Include a placeholder for a logo at the top center. Add a footer with the address and unsubscribe variables. Ensure the CSS is inline-friendly.”

Using this method, you can create a library of shells: one for weekly newsletters, one for transactional updates, and one for fundraising appeals.

Phase 2: CSS Snippets (The “In-Content” Design)

Now that you have a shell, you need to style the actual content. This is where most people get stuck. They try to use the visual editor’s settings, which are limited.

The secret is the HTML Block.

Inside Kit’s visual editor, you can insert an HTML block. While you generally want to write your text in the visual editor, you can use HTML blocks to inject specific CSS styles that “paint” the rest of the email.

You can also use inline styles directly on elements if you are willing to switch the text editor to HTML mode, but using a single <style> block at the top of your email content is often easier for maintenance.

Here are three high-impact design elements you can add to any Kit email.

1. The “Ghost” Button

Kit’s default buttons are solid blocks. Sometimes you want a secondary call to action that is less aggressive – a “ghost” button (transparent background with a border).

The Solution: Add this CSS to an HTML block at the very top of your email content (or inside your template shell <style> area):

.ghost-button {
  display: inline-block;
  padding: 12px 24px;
  border: 2px solid #000000;
  color: #000000 !important;
  text-decoration: none;
  border-radius: 4px;
  font-weight: bold;
  text-align: center;
  transition: all 0.3s ease;
}
.ghost-button:hover {
  background-color: #000000;
  color: #ffffff !important;
}

Then, whenever you want to use it, you insert an HTML block where the button should go: <a href="https://yourlink.com" class="ghost-button">Read the full story</a>

2. The Branded Blockquote

The default blockquote in Kit is usually just a gray vertical line. It is functional but boring. If you are sharing a donor testimonial or a powerful quote from your mission statement, you want it to pop.

We can transform the blockquote tag entirely using CSS.

blockquote {
  background-color: #f9f9f9;
  border-left: 5px solid #ff6b6b; /* Your Brand Accent Color */
  margin: 20px 0;
  padding: 20px;
  font-style: italic;
  font-size: 18px;
  color: #333;
  border-radius: 0 8px 8px 0;
}

If you add this to your template style, every time you click the “Quote” button in the Kit editor, it will automatically render with this new, beautiful style. You do not need to do anything extra. This is the power of Global CSS cascading.

3. The Feature Box (Callout Card)

Sometimes you need to highlight a specific section – perhaps a “Key Takeaway” or a “Urgent Action” step. A simple text background isn’t enough. You want a box with a border and a distinct background.

This requires a tiny bit of HTML in your content, but the result is worth it.

The CSS:

.callout-box {
  background-color: #eef2ff;
  border: 1px solid #c7d2fe;
  padding: 20px;
  border-radius: 8px;
  margin: 20px 0;
}
.callout-title {
  font-weight: bold;
  color: #3730a3;
  margin-top: 0;
  margin-bottom: 10px;
  font-size: 18px;
}

The HTML Usage: When you are writing your email and reach the point where you need the box, insert an HTML block:

<div class="callout-box">
  <div class="callout-title">💡 Pro Tip</div>
  This is a great place to summarize your main point or offer a specific download link that you do not want the reader to miss.
</div>

Advanced Customization: Dynamic Content Hiding

One of the most powerful features of Kit is its tagging system. You likely use tags to segment your audience for CRM & Automations. But did you know you can use those tags to alter the design of the email itself?

Kit uses the Liquid templating language. This allows you to wrap your HTML or CSS in logic statements.

For example, perhaps you have a “Premium Donor” segment. You want their emails to look slightly different – maybe with a gold border instead of a blue one.

Inside your HTML Shell, you can change the CSS based on the user’s tag:

Code snippet

<style>
  .main-content {
    border-top: 5px solid #0000ff; /* Default Blue */
  }
  
  {% if subscriber.tags contains "Premium Donor" %}
  .main-content {
    border-top: 5px solid #ffd700 !important; /* Gold for VIPs */
  }
  {% endif %}
</style>

This is a level of personalization that goes far beyond just saying “Hi {{ first_name }}.” It subconsciously reinforces the status of that donor every time they open an email.

AI Prompting for Email Design

If you are not comfortable writing CSS from scratch, you can use AI to do the heavy lifting. However, you must be specific that you are coding for email, not the web.

Here are a few “developer-grade” prompts you can use to generate assets for your Kit templates.

To Generate a Newsletter Layout:

“Create a responsive HTML email template snippet for a 3-column image gallery. It must use HTML tables for layout (no flexbox or grid) to ensure compatibility with Outlook on Windows. Images should stack vertically on mobile screens. Include inline CSS for padding and margins.”

To Generate a Typography Stack:

“I need a font stack for an email template. My brand uses ‘Montserrat’ as a primary font. Please write the CSS font-family declaration that includes ‘Montserrat’ but provides appropriate fallbacks for email clients that do not support web fonts (like Gmail). The fallback chain should end with sans-serif.”

To Fix a Broken Layout:

“I have an HTML email where the image is blowing up the width of the container on mobile. Here is the code snippet: [Paste Code]. Please rewrite this image tag to ensure it is fluid on mobile but maxes out at 600px on desktop.”

Best Practices for Asset Management

When you are customizing templates, you will be dealing with image assets – logos, social icons, and background patterns.

1. Host Images Externally: Do not rely on pasting images directly into the HTML editor if you can avoid it. Upload them to your website’s media library or a dedicated CDN. This ensures you have a permanent URL to reference in your code.
2. Optimize for Retina: Email clients on mobile devices have high-resolution screens. If your logo is displayed at 150px width, the actual image file should be 300px wide. Use HTML attributes to force the display size: <img src="logo-300px.png" width="150">.
3. Alt Text is Non-Negotiable: Many users block images by default. Your alt text should be descriptive. If you are using a button that is an image (which we generally advise against, but sometimes happens), the alt text must say “Click here to donate,” not just “button_v2.jpg”.

For more on managing digital assets and web performance, check out our resources on Google Ad Grants where we discuss the importance of landing page optimization – the same principles apply to the size and speed of your emails.

Testing Your Customizations

You cannot trust the “Preview” button in Kit alone. It renders the email in a web browser environment, which is too forgiving.

Before you send a broadcast with your new custom template to thousands of people, you must test it in real environments.

• Send a test to yourself: Check it on your phone (iOS and Android if possible) and on your desktop.
• Check Dark Mode: This is the silent killer of email design. If your text is black and your background is transparent, it will disappear when a user switches their phone to Dark Mode. Always define a background color on your text containers to prevent this, or use transparent PNGs for logos that work on both white and black backgrounds.
• Use a Testing Tool: Tools like Litmus or Email on Acid allow you to see screenshots of your email in dozens of different clients. It is a worthwhile investment if you are customizing heavily.

For a deeper check on the technical health of your domain and email deliverability, you might also want to consult tools like MXToolbox.

Conclusion

Kit is a powerful tool for monetization and audience connection, and its “limitations” regarding design are largely intentional safeguards. However, your brand does not need to suffer for the sake of deliverability.

By understanding the underlying HTML structure and using the “Shell + Snippet” strategy, you can create emails that are visually distinct, mobile-responsive, and strictly branded. You do not need to be a full-stack engineer to do this – just a little bit of curiosity and the willingness to copy-paste some code (or ask AI to write it for you) goes a long way.

If you are a mission-driven organization looking to elevate your digital presence from your website to your inbox, we are here to help. At Yeshaya.dev, we specialize in building these kinds of robust, custom systems for nonprofits. Check out our About page to learn more about our philosophy, or reach out if you are ready to upgrade your marketing infrastructure.