The Do’s and Don’ts of Custom Designed Email Templates

For an email designer, nothing compares to the feeling of wrapping up a custom designed email template that emits a premium-brand vibe. The kind that looks like it costs money. It’s what separates “just sending an email” from “sending a real brand experience”.

But dreamy-looking, tantrum-free custom designs don’t just happen. They take skill—and a set of best practices you follow like muscle memory. That’s how you build custom developed email layouts that bring some much-needed flair to your subscribers’ otherwise boring inbox.

Let’s break down the dos and don’ts of custom designed email templates—the things that make your design stand out (or fall apart).

Need more clarity on custom coded email templates? Here's what you need to see. 

The Dos of Custom Designed Email Templates

1. Do Use High-Quality, Purposeful Images

Good custom coded email templates treat images like part of the message, not just eye candy. Many marketers design with the notion that eye-grabbing images are something only fashion and luxury brands depend on. Don’t be that marketer. 

Every brand that wants to build a high ROI channel out of custom email designs can’t ignore quality images. 

Ensure you always have crisp, clear visuals to support your message and speak your brand’s visual language. 

Whether it’s a product shot, a visual metaphor, or just a little personality perk up, every image should earn its spot at the table. 

And please, stay away from those pixelated icons or overused clip art. You can do better than that.

Bonus: If the image doesn’t load, will your message still make sense? If not, rethink it. 

2. Do Prioritize Mobile-First Design

70.5% of consumers scroll emails on mobile devices. Hence, mobile-first email design is the given. 

Emails for mobile-first views are best optimized with single-column layouts, a minimum font size of 16px, and thumb-friendly buttons. Think 44px tall or more. Design for the smallest screen first, and let it scale up. 

In the words of  Megan Boshuyzen, Sr. Email Developer, Sinch Mailjet—

“Try rethinking your email templates with the beginning and the end in mind. In other words, how should an email template be displayed on the smallest and largest screens? Instead of thinking about how elements of a desktop layout will stack on mobile, consider how a responsive email could unstack or expand on larger screens.”

Goes without saying–test your custom template on multiple devices before sending. 

3. Do Optimize for Dark Mode

As more and more users view emails in dark mode, it's a must- do “do”. 

Emails designed without considering dark mode have content that blends with the background, making it unreadable. 

To prevent this mess, use transparent PNGs, test text color contrast, and check how your background and images behave when flipped from light to dark. 

4. Do Use White Space Like a Pro

White space appears empty, so we treat it as if it doesn’t need adjusting. Like, “It’s just air, right?” Yeah, no. 

The “air” is where your email content breathes and thrives. 

Otherwise, clutter occurs when every element competes for attention. Calm, clean design happens when you give your content room to stretch.

Master these:

  • Visual hierarchy

  • Consistent alignment

  • Well-defined sections

  • Balanced content-to-space ratio

5. Do Use Live Text & Buttons

Designers, we get it—you want everything to look perfect. But stuffing key messages into images? That’s just inviting trouble. 

Use live text for CTAs and important info, so it loads faster, scales better, and is easier to update.

Also, live buttons are easier to A/B test. You don’t need to rework the entire image; you just need to update the text.

6. Do Personalize with Purpose

Custom email design is about making the design your own. However, it feels customized when it addresses the individual subscriber as if it were created exclusively for them. Hence, personalization.  

To create personalized layouts and messages, segment your email list based on: 

  • Purchase behavior

  • Funnel stage

  • Location

  • First-party data (quiz results, survey responses)

Then layer on 1:1 touches, such as names, product recommendations, and localized content. 

7. Do Design with a Problem-Solver’s Mindset

Your email design can look good all day. But if it’s not useful, what’s left? Just a pretty filler.

Instead, imagine your design as a fix for subscribers' problems. Could be anything—finding the right-fit product, checking rewards points, or just feeling seen by your brand. Let your custom email template layout solve those problems. 

This could mean:

  • A personalized banner at the top

  • A reminder block about points or milestones

  • A progress bar toward a goal

8. Do Maintain Brand Consistency

Ensure your custom email templates incorporate your brand's colors, fonts, button shapes, and content layout. And the brand speak, too. 

If someone hid your logo and just saw the email, would they still recognize it as yours?

That’s the test.

Stick with recognizable templates, consistent formats, and design choices that reinforce your identity, not muddle it.

The Don’ts of Custom Designed Email Templates

1. Don’t Design Without a Plan

“Just going with the flow” might work in painting class, but not so much when you’re creating custom designed email templates. 

Start with a goal. What’s the email for? Promotion? Onboarding? Nurture? Map your content first, then build the layout to support it. 

2. Don’t Overload with Fonts, Colors, or Layouts

Custom can’t be chaotic unless you consciously decide to do it. 

If your email uses five fonts, four CTA buttons, and enough color to give a headache in readers’ eyes, they’re gone before they find the offer.

Stick to:

  • 2 font families max

  • A clear brand color palette

  • One main CTA per section (or email, ideally)

3. Don’t Use Image-Only Emails

Yes, that jaw-dropping design might look amazing as one big image. However, if the image gets blocked (which happens frequently), your email appears as a blank screen.

Plus, image-only emails:

  • Aren’t accessible

  • Don’t scale well on mobile

  • Can’t be indexed or personalized

  • Often trigger spam filters

Use live text, real HTML buttons, and ensure your email functions properly.

4. Don’t Skip Accessibility

Your subscriber might be using a screen reader. Or might be color blind. Or just trying to read your email with bad lighting on a cracked phone screen.

Design for them too:

  • Let the text rest against a contrasting background


  • Avoid color-only cues (e.g., red = error)

  • Include ALT text for images

  • Make CTAs clear and keyboard-navigable

5. Don’t Assume It’ll Look Good Everywhere

If you’ve spent enough time designing emails, you must’ve noticed that there is a lack of standardization for what an email client can or can not support. With each email client taking its own approach to email rendering, an email design that renders perfect in one client, may behave differently in another. 

That’s why you should never compromise with email testing.

There are many tools like Litmus, Email on Acid, or your ESP’s preview function to check:

  • Desktop and mobile versions.

  • Dark and light modes.

  • Different inboxes (Gmail, Outlook, Yahoo, etc.)

6. Don’t Make Users Work Extra Hard

Custom layouts can sometimes get... overdesigned. If your user has to hunt for the CTA, scroll endlessly, or play “guess what this button does,” you’ve lost them.

Keep the experience intuitive:

  • Clear visual hierarchy.

  • Obvious buttons.

  • Text that gets to the point.

7. Don’t Ignore Load Speed

Large, uncompressed images. Heavy custom fonts. Too many embedded elements.

All of this adds up to one thing: sloooow loading. And slow = skipped.

Compress images, use system fonts where possible, and remove any unnecessary elements. The faster it loads, the faster they engage.

Pro tip: Design a fallback version in case some elements don’t render.

8. Don’t Forget the Footer Details

A beautifully designed email can still get flagged—or worse, unsubscribed—if your footer is a mess.

Make sure you include:

  • A working unsubscribe link.

  • Your company’s physical address.

  • Email preferences (if applicable).

  • Proper legal disclosures. 

Wrapping Up 

Even if you’ve understood the best practices for custom designed email templates, there’s a good chance you’re thinking about the depth of the design and coding work they bring along. That’s when you bring in the right email design partner like Email Mavlers. 

Even if you have a great internal team, it doesn’t preclude you from bringing the experts to build faster, better, and stress-free. 

Good partners not only bring their specialized expertise but also continually refine their workflows based on real-world use cases.