The Data: Mobile Dominance in Email Opens
- A 2024 report by Mailjet found that 71.5% of email opens occurred on smartphones. (Mailjet)
- Other sources estimate that more than 60% of all email opens happen on mobile devices (smartphones + tablets). (AovUp (formerly Woosuite))
- Responsive/mobile‑optimized emails are shown to produce higher click rates: emails with mobile‑friendly design see a 15% increase in mobile clicks versus those that aren’t optimized. (Invesp)
- Conversely, poor mobile experience heavily penalizes brands: up to ~70% of users say they delete emails immediately if they don’t render well on a mobile device. (Invesp)
Takeaway: With the majority of opens occurring on mobile, designing for mobile devices is no longer optional—it’s essential.
Why It Matters
- First touch is often mobile
Many recipients open their email first on their phone, possibly while commuting, waiting, or on the move. If the email doesn’t display well, you lose the moment of opportunity. - Engagement & click‑through improve with mobile optimization
When emails are designed for mobile – readable text, tappable buttons, layouts that fit the screen – users are more likely to click and convert. - Brand perception and trust
A badly rendered email on mobile (e.g., tiny text, misaligned content, horizontal scrolling) reduces trust and can lead to unsubscribes or surprise negative associations with the brand. - Competitive necessity
As more brands adopt mobile‑first design, any email that doesn’t will be at a disadvantage—lower engagement, higher bounce/exit rates.
Best Practice Design Strategies for Mobile Email
Here are key design considerations to ensure your emails are optimized for mobile users:
- Responsive layout / single‑column design: Use a fluid layout that adapts to narrow screens, avoid multi‑column layouts that squeeze content. (Create The Ways)
- Readable text size & spacing: Ensure fonts are large enough for mobile readability (e.g., minimum ~16 px for body text) and adequate line spacing so readers don’t have to pinch/zoom.
- Large tappable buttons and links: Make CTAs easy to tap with a finger; recommend at least 44×44 px tappable area (as per mobile usability guidelines).
- Optimize images and load time: Mobile connections may be slower; compress images, use lighter HTML, avoid large file sizes.
- Concise subject lines & pre‑headers: On mobile devices the visible subject and pre‑header text are limited—front‑load key message and value.
- Clear focal point and CTA: On a mobile screen you have limited real estate; make sure the user can immediately see what action they should take.
- Test across devices & clients: Mobile email clients vary widely (iOS, Android, Gmail app, etc.). Use preview/testing tools to ensure rendering and interaction work across major clients. (MoldStud)
- Mobile‑first content mindset: Assume the majority of your audience is reading on mobile. Plan copy, visuals, and flow accordingly.
- Accessible design: Use sufficient colour contrast, alt text for images, and ensure navigation and buttons can be used on touch devices.
- Mobile post‑click experience: Ensure that whatever you link to (landing page, product) is also mobile‑optimized—otherwise you lose the user after the email.
Summary
In short:
- With 70%+ of email opens happening on mobile devices, mobile‑optimized design is critical for email marketing success in 2025.
- Emails that render well on mobile lead to higher engagement, clicks and conversions; those that don’t risk being deleted quickly or ignored.
- Good mobile design isn’t just about shrinking the desktop version—it requires thinking mobile‑first from layout, content, design, CTA, to post‑click experience.
Here are several case studies and industry comments illustrating how mobile‑optimized email design is crucial — especially given that 60‑70%+ of email opens now happen on smartphones — and how brands are adapting (or failing to).
Case Studies
Case Study 1: CareerBuilder (via Econsultancy)
- After switching to a responsive email design (mobile‑optimized template) the brand achieved a 15‑17% increase in open rates and a 21‑24% increase in click‑through‑rate (CTR). (Econsultancy)
- For example: their mobile opens rose (iPhone opens went from ~15% to ~18%). (Econsultancy)
- Key takeaway: Responding to the fact that a significant share of opens were on mobile, the design change had measurable uplift in engagement.
Case Study 2: Tsubo (Footwear Brand under Deckers Brands)
- When Tsubo transitioned to mobile‑optimized/responsive email templates (recognising that 35‑65% of their subscribers opened on mobile) they saw ~10% increase in CTR. (Econsultancy)
- Insight: Even a modest improvement in mobile design can translate into meaningful lift in engagement.
Case Study 3: Industry‑wide data from Invesp
- Invesp reports that “more than 2/3 of emails are being opened on smartphones and tablets.” (Invesp)
- They also found that responsive (mobile‑optimized) emails achieved a 15% increase in unique clicks for mobile users (from 2.7% to 3.3%). (Invesp)
- The cost of neglecting mobile: about 70% of consumers delete emails immediately if they don’t render well on their mobile device. (Invesp)
Industry Comments & Insights
- From an article on mobile‑first email design:
“According to Litmus’ study of more than one billion monthly email‑opens, a whopping 54% of emails were viewed on mobile devices and only 19% were viewed on desktop.” (Email Mastery)
This emphasises the scale of the mobile‑open majority. - From Smart Insights:
“Despite the increase in number of mobile devices, only half of marketers are designing email with mobile in mind… there is a huge drop in the percentage who are clicking through.” (Smart Insights)
This highlights the gap between open behaviour and click behaviour when mobile design is overlooked. - Practitioner comment from Reddit:
“In 2025, the majority of email opens are on mobile (some niches see 70%+). If your emails don’t load fast, use large readable text, and have tappable CTAs, you’re basically throwing away conversions.” (Reddit)
This reinforces that for mobile‑heavy audiences, design flaws directly harm results.
Key Themes & Implications
- Mobile dominates opens: The data suggests that more than half — in some reports ~70% — of email opens are happening on mobile phones. Failing here means missing the majority of engagements.
- Design matters for clicks, not just opens: While many opens happen on mobile, click‑through and conversion often suffer when the email wasn’t optimized for mobile (e.g., hard to read, tiny CTAs, horizontal scroll).
- Responsive templates and mobile‑first design yield measurable uplift: As seen in the CareerBuilder and Tsubo examples, redesigning for mobile leads to higher CTRs, better mobile engagement.
- Neglecting mobile design carries risk: Emails that don’t render well may be deleted quickly, unsubscribed, or ignored altogether. The Invesp stat that ~70% of users will delete poorly rendered mobile email underlines this risk.
- Design best‑practices must evolve: Important design considerations include single‑column layouts, large tappable buttons, readable fonts, minimal horizontal scroll, lightweight load, and fast render speed.
- Mobile first ≠ desktop second: Many emails are still designed for desktop and then “shrunk” to mobile. True mobile‑first means designing for the phone experience and letting it adapt to desktop.
- Measurement & benchmarking matter: Brands should track mobile opens, mobile click‑through, device share of opens and clicks — and benchmark mobile vs desktop performance to identify gaps.
- Audience behaviour nuances: While mobile dominates opens, some deeper conversions may still happen on desktop — so designing the mobile → later desktop journey may matter too. (See the Smashing Magazine commentary) (Smashing Magazine)