Why Mailto Links Cannot Send Attachments (RFC 6068 Explained)

If you’ve ever tried to create a mailto link that automatically attaches a file, you’ve probably discovered it doesn’t work. This isn’t a browser bug or a missing feature—it’s by design.

Let’s dive into the technical reasons and explore practical alternatives.

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The Short Answer

No, mailto links cannot include attachments. This is explicitly defined in RFC 6068, the official specification for mailto URIs.

The “mailto” URI scheme is used to designate the Internet mailing address of an individual or service. It is defined to support the simple composition of a message and does not include any mechanisms for attaching files.

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Understanding RFC 6068

RFC 6068 replaced the older RFC 2368 in 2010. It defines what a valid mailto link can contain:

✅ What Mailto Links CAN Do

Parameter	Description	Example
to	Recipient email	mailto:[email protected]
cc	Carbon copy	[email protected]
bcc	Blind carbon copy	[email protected]
subject	Email subject line	?subject=Hello%20World
body	Pre-filled message body	?body=Hi%20there%0A%0AThanks

❌ What Mailto Links CANNOT Do

Feature	Status	Reason
Attachments	Not supported	Security risk
Custom headers	Limited	Only safe headers allowed
HTML body	Not supported	Must be plain text
Inline images	Not supported	No binary data support

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Why No Attachments? Security.

The prohibition on attachments is a critical security feature. Here’s why:

1. Prevents Malicious File Distribution

If mailto links could attach files, a malicious website could:

• Attach executable malware
• Include phishing documents
• Silently embed viruses

<!-- Imagine if this worked (it doesn't!) -->
<a href="mailto:[email protected]?attach=/path/to/malware.exe">
  Send Resume
</a>

The user might click this thinking they’re sending a resume, but actually sending malware.

2. No Access to Local Filesystem

Mailto links run in the browser context. Browsers are sandboxed and cannot access local files without explicit user permission. An attachment parameter would require:

• Reading files from disk (security violation)
• Uploading binary data via URL (impractical)

3. Email Client Limitations

Even if the protocol allowed it, email clients would need to:

• Validate the file path
• Handle file size limits
• Support multipart MIME encoding

This complexity is better handled by dedicated file-sharing solutions.

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What About the “attachment” Trick?

You may have seen URLs like:

<!-- This does NOT work -->
<a href="mailto:[email protected]?attachment=file.pdf">Send</a>

This is a myth. No email client supports this. The attachment parameter is not defined in RFC 6068 and is universally ignored.

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Alternatives to Mailto Attachments

1. Cloud Storage Links

The modern solution is to share files via cloud links:

<a href="mailto:[email protected]?subject=Document%20for%20Review&body=Please%20review%20the%20document%20here%3A%20https%3A%2F%2Fdrive.google.com%2Ffile%2Fd%2F...">
  Send Document
</a>

Benefits:

• ✅ Works with all email clients
• ✅ No file size limits
• ✅ Trackable (view counts, access logs)
• ✅ Secure (expiring links, password protection)

2. File Upload Forms

For user-submitted files, use a proper web form:

<form action="/api/submit" method="POST" enctype="multipart/form-data">
  <input type="email" name="email" placeholder="Your email">
  <input type="file" name="attachment" accept=".pdf,.doc">
  <button type="submit">Submit</button>
</form>

Benefits:

• ✅ Full control over file types
• ✅ Server-side validation
• ✅ Automated email sending with attachments

3. Pre-Generated Download Links

If users need to send a specific file, generate a download link:

<a href="mailto:[email protected]?subject=Job%20Application&body=Please%20find%20my%20resume%20at%3A%0Ahttps%3A%2F%2Fyoursite.com%2Fresumes%2Fabc123.pdf">
  Apply Now
</a>

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Testing Your Mailto Links

Use our Free Mailto Link Generator to create properly encoded mailto links. Our tool:

• ✅ Automatically encodes special characters
• ✅ Shows character count (important for Outlook’s 2000-char limit)
• ✅ Generates QR codes for mobile
• ✅ Warns about unsupported features

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Summary

Question	Answer
Can mailto links have attachments?	No
Is this a browser bug?	No, it’s by design (RFC 6068)
Why not?	Security: prevents malware distribution
Best alternative?	Cloud storage links (Google Drive, Dropbox)

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Related Reading

• Complete Mailto Syntax Guide
• RFC 6068 BCC and CC Parameters Guide
• Mailto Link Generator

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Last Updated: December 2025