Top 5 Email Clients in 2025 and How They Handle Mailto Links

As developers, we often assume a mailto link just “works.” But in 2025, the landscape of email clients is more fragmented than ever. Different clients handle URL encoding, character limits, and attachments differently.

Here is a breakdown of the top 5 email clients in 2025 and what you need to know about them.

1. Gmail (Web & Mobile)

Market Share: ~30%

Gmail remains the king of email.

• Mailto Behavior: Opens a compose window within the browser (if set as default handler) or the Gmail app on mobile.
• Quirks:
  • Excellent support for standard parameters (subject, body, cc, bcc).
  • Warning: If the URL is too long (>2000 chars), it might truncate silently or fail to open on some mobile versions.

Official documentation: Gmail URL scheme for mobile

2. Apple Mail (iOS & macOS)

Market Share: ~58% (combined mobile/desktop)

Dominant on mobile devices.

• Mailto Behavior: Opens the native Mail app instantly.
• Quirks:
  • Extremely robust. Handles very long URLs better than most.
  • Supports rich text pasting if the user copies content, but body parameter is plain text only.
  • Follows RFC 6068 mailto URI specification very closely.

3. Microsoft Outlook (Desktop & Web)

Market Share: ~4% (but higher in B2B)

The standard for enterprise.

• Mailto Behavior: Opens the Outlook desktop app or OWA.
• Quirks:
  • The 2083 Character Limit: Older versions of Outlook (and even some modern configurations) have a strict URL length limit. Exceeding this causes the link to do nothing when clicked.
  • Encoding: Very sensitive to improper encoding. Always use %20 for spaces.

Learn more: URL encoding best practices for mailto links.

4. Yahoo! Mail

Market Share: ~2.5%

Still popular among legacy users.

• Mailto Behavior: Web-based handler.
• Quirks:
  • Similar to Gmail but less forgiving with malformed parameters.
  • Percent-encoding is critical for special characters.

5. ProtonMail & Tutanota (Privacy-Focused)

Market Share: Rising (<1% but significant in tech)

• Mailto Behavior: often requires a browser extension or desktop bridge to handle system-wide mailto links.
• Quirks:
  • Security-focused. Might strip certain parameters if they look suspicious (though standard subject/body are usually fine).

Summary Table

Client	Max URL Length	Encoding Support	Mobile Experience
Gmail	~2000 chars	Excellent	Excellent
Apple Mail	>2000 chars	Excellent	Native/Fast
Outlook	~2000 chars	Strict	Good
Yahoo	~2000 chars	Good	Average

The Developer’s Takeaway

To ensure 100% compatibility across all these clients in 2025:

1. Keep it Short: Try to keep your generated mailto links under 2000 characters to satisfy Outlook.
2. Encode Everything: Never use raw spaces or special characters. Learn proper encoding techniques.
3. Test on Mobile: 60%+ of emails are opened on mobile devices.
4. Use a Generator: Manual coding increases error rates. Compare the approaches.

Need a tool that handles these quirks for you? Try MailtoMaker – we test against all major clients so you don’t have to.

Related Resources:

• How to Add a Mailto Link in HTML - Complete syntax guide
• Stop Using mailto: for Forms - Common mistakes
• Browse All Articles
• Developer Cheatsheets