# How to Determine the Email Client of Your Recipients

Get insights into email client usage data to understand what your customer base uses and discover how you can use it to optimize your email campaigns.

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## Table of contents

- Why email client data matters to marketers
- How to check email client insights
- What do you do once you’ve gathered email client data?
- Final thoughts

When you send an email campaign, how it appears in your recipient’s inbox depends heavily on which email client they’re using. Whether it’s Gmail, Outlook, Apple Mail, or another platform, each one has its quirks in how it renders HTML, supports features like AMP, and handles interactive elements.

If you want to check which email client your subscribers are using, keep reading this guide, where we will discuss practical methods for tracking email client usage and how to use that information to improve your campaign performance.

## Why email client data matters to marketers

Understanding which email clients your audience uses can make a big difference in how well your campaigns perform.

-   Improved design decisions: Knowing the most common clients lets you tailor layouts and features so everything looks great. No more broken designs in Outlook or unsupported elements in Apple Mail.
    
-   Targeted testing and QA: Testing every email on every client is time-consuming. By focusing on the clients most used by your audience, you catch the most critical rendering issues while saving time.
    
-   Better deliverability insights: Some clients behave differently with images, links, or scripts, which can affect deliverability and tracking accuracy. Knowing client usage helps you interpret your metrics correctly.
    

## How to check email client insights

There are several ways to gather which email clients your audience uses, ranging from simple analytics to more advanced techniques. Let's take a look at some common ones

1.  ### Using email tracking tools
    

The easiest and most reliable way to see which clients your recipients are using is through [email tracking tools](https://www.mailmodo.com/guides/email-tracking/). Platforms like Mailmodo show how your opens are distributed across various clients, helping you see where most engagement comes from.

These tools typically rely on tracking pixels or analyzing click behavior to estimate the client. Over time, you can see trends, compare client usage, and identify which platforms are driving the most engagement.

2.  ### Examining email header information
    

If someone replies to your message, email headers can sometimes reveal which client was used. Look for fields like User-Agent or X-Mailer in the header, which can indicate the software or platform that opened the email.

In Gmail or Outlook, you can open an email and select “More” or “Show Original” to inspect the header information. While this method doesn’t always guarantee accurate recipient-level data, it can provide useful hints, especially when combined with other tracking methods.

3.  ### UTM parameters & links
    

Another indirect method is UTM tagging your email links. By appending a client-specific parameter to your URLs, you can track which devices or clients are driving traffic to your landing pages.

When analyzing your click data, you can see patterns that reveal which clients are being used. This is especially helpful if you want to correlate engagement with specific email platforms.

4.  ### Email client market share data
    

Even without precise recipient-level tracking, you can use market share data to make informed decisions. Resources like Litmus report which clients are most popular globally or by region.

Knowing the general trends allows you to prioritize your design efforts for the clients most likely to be used by your audience. For example, if Gmail dominates your target region, you can optimize features like [AMP](https://www.mailmodo.com/guides/amp-for-email/) and interactive blocks for Gmail first.

  

## What do you do once you’ve gathered email client data?

Once you’ve gathered the data, here are a few things for you to do:

-   Prioritize your design strategy: If Gmail dominates, it makes sense to include AMP or [interactive](https://www.mailmodo.com/guides/interactive-emails/) features. If Outlook is common, opt for more static, compatibility-first layouts.
    
-   Adapt your fallback planning: Make sure fallback content is optimized for the least capable clients.
    
-   Drive design QA testing: Focus [testing efforts](https://www.mailmodo.com/guides/email-testing/) on the clients that constitute the biggest chunk of your audience.
    

## Final thoughts

Understanding email client usage is just the first step toward smarter campaigns. Once you know which platforms dominate your audience, you can start designing emails that work reliably for most recipients while experimenting with advanced features for capable clients. This insight allows you to plan campaigns strategically rather than guessing what will render correctly.

The next step is testing and iteration. By focusing QA efforts on the most-used clients and monitoring engagement trends, you can fine-tune layouts, interactive elements, and fallback content over time. This continuous approach ensures your emails evolve alongside your audience’s habits and technology, keeping your campaigns effective and future-proof.

## Frequently Asked Questions

### How accurate are email client detection tools?



 They are generally reliable for high-level trends, since they use tracking pixels, headers, and click data. Accuracy can vary when clients block images or mask user-agent details.

### Why do some tools report email client data differently?


Each tool relies on its own mix of pixels, user-agent info, and redirects. When privacy protections interfere, each platform fills in gaps differently, which leads to variations.

### Can privacy settings block email client tracking?


 Yes. Image blocking, VPN routing, and anti-tracking features can limit data collection or replace real client details with generic values.
 

### What is the difference between device data and client data?

Client data refers to the software used to read the email, while device data refers to the hardware. Both matter for design choices.


### How often should marketers review email client trends?

A quarterly review works well for most teams. If your audience shifts quickly, a monthly check helps you stay aligned with current behavior.

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