Definition
Email client market share represents the proportional distribution of how recipients read email across different email clients and devices. The primary data sources are Litmus Email Analytics and Email on Acid, which aggregate data from millions of email opens tracked through embedded pixels in campaigns sent through their platforms. Typical distribution shows Gmail at 30–35% share depending on audience, Apple Mail (including iOS Mail and macOS Mail) at 25–30%, Outlook at 10–15%, Yahoo Mail at 5–8%, and Samsung Mail at 3–5%. Smaller but notable clients include Proton Mail, which has been growing steadily, and various regional Chinese and Russian clients.
Market share varies significantly by audience type and industry. Business-to-consumer campaigns targeting general consumers see higher Apple Mail and Gmail representation because consumers commonly use the default mail app on their phones or free webmail services. Business-to-business campaigns see higher Outlook and Office 365 representation because corporate environments standardise on Microsoft. Geographic variation is also significant: Apple Mail share is higher in North America and Western Europe, while Gmail dominates in emerging markets where Android devices are prevalent.
Mobile versus desktop versus webmail distribution is a critical dimension of market share data. Mobile email opens now account for approximately 40–60% of all opens depending on the audience, with desktop at 20–30% and webmail at 20–30%. These ratios shift over time; mobile share has grown steadily over the past decade while desktop has declined. Understanding the device distribution within each email client enables senders to prioritise responsive design, touch-friendly calls to action, and load-time optimisation for mobile networks.
Best Practices
Use market share data to prioritise testing and optimisation efforts. Focus on the top three clients that represent your specific audience, not the global averages.
Segment your market share analysis by campaign type and audience segment. A B2B campaign may have 60% Outlook share, while a B2C campaign for the same brand may have 35% Gmail and 30% Apple Mail.
Re-evaluate market share at least quarterly. The email client landscape shifts as new versions release, corporate policies change, and user preferences evolve.
Design for mobile first if your audience shows mobile open rates above 40%. Prioritise single-column layouts, legible font sizes, and touch-optimised button sizes.
Track market share trends by device (mobile, desktop, webmail) separately from client identity. Mobile Apple Mail and desktop Apple Mail have different rendering capabilities and user contexts.
Share market share insights with design and content teams so they understand which clients and devices to optimise for in their creative decisions.
Related Glossary Terms
Email Bulk
Bulk email classification distinguishes mass commercial messages from transactional emails, with specific authentication requirements for senders over 5,000 daily.
Email Inbox Provider
Major email inbox providers compared by market share, filtering behaviour, authentication requirements, and feature differences.
Frequently Asked Questions
The most cited sources are Litmus Email Analytics and Email on Acid, which track millions of email opens per month through open-rate tracking pixels. These data sets are opt-in from their customers and may over-represent North American and European audiences. Industry-specific benchmarks are also available from email service providers.
Apple Mail open rates have been artificially inflated since 2021 when Apple introduced Mail Privacy Protection (MPP). MPP preloads email content in the background, causing open-rate tracking pixels to fire even when the recipient has not actually viewed the email. This has increased Apple Mail's measured share by 5–10 percentage points in many reports.
High mobile share requires responsive or mobile-optimised email design with single-column layouts, font sizes of at least 14px for body text, touch-friendly buttons (minimum 44x44 pixels), and careful attention to load times. Desktop-dominant audiences allow for more complex multi-column layouts.
Outlook's overall share has declined over the past decade, particularly as mobile email usage has grown and Gmail has expanded. However, Outlook remains dominant in corporate and B2B segments. The new Outlook client moving to Chromium may affect share by improving the user experience.
Most email service providers offer client-level reporting in their analytics dashboards. Check the email client or device breakdown in your ESP's reporting tool for your own sends. This data is more relevant for your optimisation decisions than industry-wide averages.