What is an email client?

Email client

An email client is software that lets you send, receive, and organize email without opening a web browser. It connects to your email provider's servers, downloads messages to your device, and gives you a dedicated interface for managing your inbox.

You might already use one without realizing it. Apple Mail on your iPhone, Outlook on your work computer, Thunderbird on your laptop: these are all email clients. They pull messages from services like Gmail, Yahoo, or your company's Exchange server and display them in one place.

How email clients work

When you set up an email client, you're connecting it to your email provider using specific protocols. The client doesn't store your email on its own servers; it retrieves messages from wherever your email actually lives.

Two protocols handle incoming mail:

• POP3 downloads messages to your device and typically removes them from the server. Good for offline access, but your email only exists in one place.
• IMAP syncs messages across devices. Delete an email on your phone, and it disappears from your laptop too. Most modern setups use IMAP.

For sending mail, clients use SMTP to route your messages through your provider's outgoing servers.

Email client vs. webmail

Webmail is what you use when you log into Gmail.com or Outlook.com through a browser. An email client is a standalone application installed on your device.

The practical differences matter:

• Offline access: Email clients let you read and draft messages without an internet connection. Webmail requires you to be online.
• Multiple accounts: Clients can pull mail from Gmail, Outlook, and your work email into a single inbox. Webmail keeps each account separate.
• Speed: Native applications typically load faster than browser tabs.
• Features: Clients often include calendars, contact management, and task lists built in.

Webmail wins on convenience, with no installation required and access from any device with a browser. Email clients win on power and flexibility.

Popular email clients

Desktop and mobile options span free and paid:

• Microsoft Outlook: The standard for business environments, especially those using Microsoft 365
• Apple Mail: Built into macOS and iOS, handles iCloud and third-party accounts
• Mozilla Thunderbird: Free, open-source, and highly customizable with add-ons
• Spark: Focuses on smart inbox features and team collaboration
• eM Client: Windows and Mac client with calendar and chat integration

For mobile, most people use the default mail app on their phone or download Gmail, Outlook, or Spark from their app store.

Why email clients matter for marketers

If you send email marketing campaigns, your subscribers open those messages in email clients. Each client renders HTML and CSS differently, so an email that looks perfect in Gmail might break in Outlook.

This is why testing across clients matters. Tools like Litmus let you preview how your campaigns appear in dozens of email clients before you hit send.

Understanding which clients your audience uses, data you can pull from your email reporting, helps you prioritize which rendering quirks to fix first.

FAQs

What's the difference between an email client and an email server?
An email client is the software you interact with. An email server is the computer that stores and routes your messages. The client talks to the server to send and retrieve mail.

Is Gmail an email client?
Gmail.com is webmail, not a client. However, the Gmail mobile app functions as an email client since it's installed software that connects to Google's servers.

Do I need an email client if I use webmail?
Not necessarily. If you only check one email account and always have internet access, webmail works fine. Email clients become valuable when you manage multiple accounts or need offline access.

Can email clients work with any email provider?
Most clients support standard protocols like IMAP and SMTP, so they work with nearly any provider. Some providers also offer dedicated integrations for smoother setup.

Ready to see how your campaigns look across every email client? Start your free ActiveCampaign trial and build emails that render beautifully everywhere.