Custom fonts in email marketing
Valeria Jiménez
December 15, 2025
Whether you call it “branding detail” or “the little things,” font choice in email marketing matters more than many marketers realize. But using a custom font instead of sticking to the classics brings tradeoffs. In this post, we’ll unpack when custom fonts make sense, when they don’t, and how to use them without compromising readability or deliverability.
Why fonts matter in email marketing
Typography isn’t just decoration. It guides how easily recipients read, understand, and emotionally respond to your message. In formal typographic theory, legibility refers to how easily letterforms can be distinguished, while readability refers to how comfortably a reader can process larger bodies of text.
A classic screen-reading study compared two fonts, one serif and one sans-serif, and concluded that a sans-serif screen font optimized for on-screen display (in that case, Verdana) delivered significantly better comprehension and reading speed than a serif alternative.
For email marketing, this matters. If subscribers struggle to read your message because the font is too dense, small, or unfamiliar, even the clearest copy can lose impact. Good typography supports engagement, accessibility, and lets recipients focus on your message rather than deciphering it.
Custom fonts vs email-safe fonts: tradeoffs
Email-safe (web-safe) fonts: the positives
Reliable rendering across nearly all email clients and devices.
Greater consistency and predictability; what you design is what most of your subscribers will see.
Lower risk of layout issues, broken bullets/lists or misaligned elements due to font fallback.
Simplified development and QA: no need to test every client or worry about external font loading failures.
Common choices include classics like Arial, Verdana, Helvetica, Tahoma, and others that are pre-installed or widely available on operating systems.
Custom / web fonts: the risks
Many popular email clients simply do not support custom fonts, so your design may collapse to a fallback without notice.
Rendering differences across clients can impact layout: spacing might shift, text may wrap differently, preview text may truncate, or mobile responsiveness might break.
The visual gains are often subtle. Few readers can reliably tell a premium typeface from a standard one, but almost anyone can notice when the email is hard to read. “If it’s beautiful and unreadable, that’s an issue,” says one industry guideline.
Because of all this, many reputable email-design resources advise that, if you choose custom fonts, you must always include a well-matched fallback and thoroughly test across email clients.
What research says about readability and cognition
Outside of email marketing, scientific research on typography encourages caution:
A 2021 study by AdaptiFont used a generative-font model and Bayesian optimization to show that typefaces can significantly influence reading speed, depending on the user. The study found that some fonts dramatically improved reading speed for certain readers.
Recent efforts like the Cognitive Type Project (2024) explore how type design affects cognition, readability, perceived beauty, and memorability. Their findings reinforce that typography choices change not only how easily people read but how they feel about what they read.
The longstanding research tradition initiated by Miles Tinker demonstrated that typography variables: font size, style (serif versus sans-serif), line spacing (leading), line length; systematically affect reading speed and eye movements.
In short: fonts are not just superficial design, they influence comprehension, cognitive load, reading speed, and user experience.
When custom fonts make sense, and when to avoid them
✔️ Go for custom fonts when:
Brand identity is central to the experience. If your brand voice relies on a distinctive typographic “tone,” and you’re willing to invest in testing and fallback strategy, custom fonts can reinforce brand recognition and differentiation.
You know your audience’s email client preferences. If your subscriber base predominantly uses clients that support web fonts (for example, Apple Mail, certain mobile clients), custom fonts may render reliably.
You minimize body text or use fonts primarily in headers, hero banners, or small blocks, reducing risk of readability or layout issues for core content.
🚫 Avoid custom fonts when:
Your email contains long blocks of copy, dense content, or needs maximum readability. In these cases, sticking to proven email-safe fonts ensures clarity and accessibility.
Your audience includes a broad mix of email clients (desktop, mobile, webmail). Inconsistent font rendering may degrade the user experience for a sizable portion of subscribers.
You lack the resources (time, QA bandwidth, or dev effort) to test across major clients and provide thoughtful fallback styling.
Best practices if you do use custom fonts
Always include fallback fonts in your font-family stack, matching the fallback to your brand’s tone as closely as possible.
Optimize typographic properties: ensure adequate line spacing (leading), line length, contrast, and letter spacing (tracking) so text remains easy to read.
Test across email clients and devices—especially mobile—before rolling out to your full list.
Use custom fonts selectively (headers, accents) rather than for all body copy.
Monitor engagement metrics post-send (opens, clicks, bounce-backs, readability signals) to detect whether typography affects performance.
Conclusion
Custom fonts can be a powerful tool for brand differentiation, but only if used carefully. For many e-commerce and digital brands, sticking with email-safe fonts is the safer, more scalable path: you safeguard readability, accessibility, and cross-client consistency. And when you do opt for custom fonts, approach with rigor: fallback fonts, strong typographic hygiene, and cross-client testing.
As you build your email templates and automation flows, think of typography not as decoration, but as part of the core user experience.
