How to Attach Email to Email: Complete Guide for 2026

Why Attach an Email Instead of Forwarding?

Before diving into the how-to, it’s important to understand when attaching an email makes more sense than simply forwarding:

• Preserves complete headers: Full routing information, authentication results, and server data remain intact
• Spam reporting: Security teams need original headers to trace malicious senders
• Legal documentation: Courts and compliance officers require unmodified email evidence
• Multiple message sharing: Attach several related emails to provide full context
• Prevents inline editing: Recipients can verify the message hasn’t been altered

When you forward an email, the original headers are often stripped or modified, and the content becomes part of your new message body. Attaching preserves the email as a distinct, standalone file.

Prerequisites

Before you begin, ensure you have:

• Access to your email client (desktop application or web browser)
• The email(s) you want to attach available in your inbox or folders
• Sufficient attachment size limits (most services allow 25-50MB total)
• For encrypted services: recipient’s public key if using PGP (optional but recommended)

Method 1: Gmail (Web Interface)

Gmail’s web interface makes attaching emails straightforward, though the feature isn’t immediately obvious.

Step 1: Enable the Right View

Ensure you’re using the standard Gmail view (not basic HTML). The option only works in the full interface.

Step 2: Select Email(s) to Attach

1. Navigate to your inbox or folder containing the target email
2. Hover over the email you want to attach (don’t open it)
3. Click the checkbox on the left side of the email row
4. For multiple emails: check multiple boxes while holding Shift for consecutive emails

Step 3: Drag and Drop

1. With email(s) selected, click and hold on any selected email
2. Open a new compose window (click “Compose” in another tab or window)
3. Drag the selected email(s) into the body of the new message
4. Release when you see the attachment indicator appear

The emails will attach as individual .eml files, preserving all headers and content.

Alternative: Three-Dot Menu Method

1. Open the email you want to attach
2. Click the three-dot menu icon (⋮) in the top right
3. Select “Forward as attachment”
4. A new compose window opens with the email already attached

Method 2: Outlook (Desktop Client)

Microsoft Outlook for Windows and Mac offers robust email attachment capabilities, saving messages as .msg files.

Windows Steps

1. Open Outlook and navigate to the folder with your target email
2. Create a new email message (Ctrl+N or click “New Email”)
3. Arrange windows so you can see both the new message and your inbox
4. Click and drag the email from your inbox directly into the body or attachment area of the new message
5. The email attaches as a .msg file with its original subject as the filename

Mac Steps

1. Select the email(s) you want to attach in your mailbox view
2. Click “Message” in the menu bar
3. Select “Forward as Attachment” (or press Option+Cmd+F)
4. A new compose window opens with the selected email(s) attached

Attaching Multiple Emails

Hold Ctrl (Windows) or Cmd (Mac) while clicking multiple emails, then drag them all at once into your new message. Each becomes a separate .msg attachment.

Method 3: Thunderbird

Mozilla Thunderbird is a popular open-source email client with strong privacy features and straightforward email attachment functionality.

1. Open Thunderbird and select the email(s) you want to attach
2. Right-click on the selected email
3. Choose “Forward As” → “Attachment”
4. Alternatively, select multiple emails, then go to Message → Forward As → Attachment
5. A new compose window opens with emails attached as .eml files

Thunderbird preserves full headers and works seamlessly with both standard and encrypted email accounts.

Method 4: Privacy-Focused Email Services

Privacy-conscious users often rely on encrypted email providers. Here’s how major services handle email attachments:

ProtonMail

ProtonMail supports attaching emails through their web interface:

1. Log into ProtonMail at protonmail.com
2. Navigate to the email you want to attach
3. Open the email and click the three-dot menu (⋮)
4. Select “More” → “View source”
5. Copy the raw email source
6. Compose a new message
7. Create a .txt or .eml file with the source content and attach it traditionally

Alternatively, use ProtonMail Bridge with Thunderbird or Outlook for native email attachment support. Bridge creates a local IMAP/SMTP server that decrypts messages for desktop clients while maintaining end-to-end encryption during transmission.

Onion Mail

Onion Mail operates over Tor and supports standard email protocols with strong privacy protections:

1. Access your Onion Mail account via their .onion address or clearnet gateway
2. For webmail users: Download the email you want to attach (right-click → “Save as” → .eml format)
3. Compose a new message
4. Attach the saved .eml file like any other attachment
5. For maximum privacy: encrypt the attachment with recipient’s PGP key before sending

Onion Mail’s PGP integration allows you to attach encrypted emails and re-encrypt them for new recipients, useful when forwarding sensitive correspondence through additional privacy layers.

Tuta (Tutanota)

Tuta uses proprietary encryption that encrypts subject lines and doesn’t support traditional .eml exports:

1. Open the email you want to share
2. Use the “Forward” function (which includes full headers in the body)
3. For preservation: take a screenshot or copy full text including headers
4. Consider exporting your Tuta account periodically for backup purposes

Tuta’s architecture prioritizes security over interoperability, making traditional email attachment more difficult by design.

Mailfence

Mailfence supports OpenPGP and standard protocols:

1. Log into Mailfence webmail
2. Open the target email
3. Click “More” → “Download” to save as .eml file
4. Compose new message and attach the downloaded .eml file
5. Optional: sign or encrypt the entire message with OpenPGP

Method 5: Apple Mail (macOS/iOS)

macOS Mail

1. Open Mail and select the email(s) you want to attach
2. Click “Message” in the menu bar
3. Select “Forward as Attachment”
4. Or drag emails directly from your mailbox into a new compose window

iOS Mail (iPhone/iPad)

iOS Mail has limited support for attaching complete emails:

1. Open the email you want to attach
2. Tap the forward arrow icon
3. iOS will inline-forward the content (doesn’t preserve as .eml)
4. For true attachment: use the Files app to save a screenshot or forwarded copy first

Note: Mobile email clients generally lack full email attachment capabilities. For important use cases (legal, security), use desktop clients.

Method 6: Export and Attach Manually

When your email client doesn’t support direct attachment, export emails manually:

Universal Export Method

1. Open the email you want to attach
2. Look for “View Source,” “Show Original,” or “Download” options
3. Save the email as a .eml or .txt file to your computer
4. Compose a new email
5. Attach the saved file using the standard attachment button

Example: Saving Gmail Message Source

1. Open the email in Gmail
2. Click the three-dot menu (⋮)
3. Select “Show original”
4. Click “Download original” in the new window
5. A .eml file downloads to your computer
6. Attach this file to any new email

Understanding Email File Formats

Attached emails typically use these formats:

• .eml: Standard email format readable by most clients (Thunderbird, Windows Mail, Apple Mail)
• .msg: Microsoft Outlook proprietary format; requires Outlook or third-party viewers
• .mbox: Unix mailbox format containing multiple emails
• .txt: Plain text source with full headers; universally readable but no formatting

For maximum compatibility, .eml format is recommended. Recipients can double-click to open in their default email client.

Troubleshooting Common Issues

Issue: “Drag and Drop Doesn’t Work”

Solutions:

• Ensure JavaScript is enabled in your browser
• Try the alternative menu method (Forward as Attachment)
• Check browser compatibility (Chrome, Firefox, and Edge work best)
• Disable browser extensions that might interfere with drag-and-drop

Issue: “Attachment Size Too Large”

Solutions:

• Remove large attachments from the original email before attaching
• Compress multiple emails into a .zip archive
• Use cloud storage links for very large email collections
• Check your provider’s limits: Gmail (25MB), Outlook (20MB), Onion Mail

Issue: “.msg Files Won’t Open”

Solutions:

• Install a .msg viewer (free tools available for Windows, Mac, Linux)
• Ask the sender to resend as .eml format instead
• Use online .msg converters (note privacy implications)
• Open in Microsoft Outlook or Outlook.com

Issue: “Headers Are Missing”

Solutions:

• Verify you used “Forward as Attachment” not regular “Forward”
• Check if your email service strips headers (some privacy services do this)
• Export using “Show Original” or “View Source” methods
• Contact your email provider about header preservation policies

Issue: “Recipients Can’t Open Encrypted Attachments”

Solutions:

• Ensure recipient has your PGP public key imported
• Send encryption instructions or public key in a separate message
• Consider using encrypted services like Onion Mail or ProtonMail where encryption is automatic
• For sensitive content, verify recipient’s encryption capabilities first

Security and Privacy Considerations

When attaching emails, especially sensitive ones, consider these privacy factors:

Metadata Exposure

Attached emails contain full headers revealing:

• IP addresses of senders
• Email server routing information
• Timestamps down to the second
• Email client and device information

If privacy is critical, redact headers or use services like Onion Mail that minimize metadata collection from the start.

Encryption Best Practices

1. Encrypt the entire message: Use PGP to encrypt both your message body and attachments
2. Verify recipient identity: Confirm public keys through secondary channels
3. Use end-to-end encrypted services: ProtonMail, Tuta, and Onion Mail encrypt by default
4. Consider threat model: Government surveillance, corporate espionage, or casual privacy needs require different approaches

Legal and Compliance

For legal or compliance purposes:

• Never modify email content before attaching
• Preserve all headers and metadata
• Use .eml format for court admissibility
• Maintain chain of custody documentation
• Consider using services with compliance features (Mailfence offers digital signatures)

Advanced Tips and Workflows

Batch Processing Multiple Emails

When attaching many emails:

# Thunderbird: Select multiple with Ctrl+Click (Windows) or Cmd+Click (Mac)
# Then Message → Forward As → Attachment

# Gmail: Use search operators to find related emails
from:sender@example.com subject:"project alpha"
# Select all results, drag into new compose window

Automating Email Attachment with Filters

Some email clients allow automated forwarding as attachment:

1. Create a filter/rule in your email client
2. Set condition (e.g., emails from specific sender)
3. Set action to “Forward as attachment” to designated address
4. Useful for automated reporting or archiving workflows

Cross-Platform Compatibility

To ensure attachments work across all platforms:

• Use .eml format instead of .msg when possible
• Test with recipients on different clients before bulk sending
• Include instructions for opening attached emails
• Provide alternative access methods (screenshots, PDF exports)

Email Attachment Capabilities by Service (2026)

Conclusion

Attaching emails to emails is a fundamental skill for anyone handling sensitive correspondence, managing legal matters, reporting security issues, or simply organizing complex email threads. While the process varies across different email clients and services, the core concept remains the same: preserve the original message with full headers and metadata intact.

For everyday users, mainstream services like Gmail and Outlook offer straightforward drag-and-drop functionality. Privacy-conscious users should consider how their email provider handles attachments and metadata—services like Onion Mail, ProtonMail, and Mailfence offer varying approaches to balancing usability with privacy protection.

Next Steps

• Practice attaching emails in your primary email client using the methods above
• Verify recipients can successfully open your attached emails
• If handling sensitive information, investigate PGP encryption and privacy-focused email services
• Set up desktop email clients (Thunderbird, Outlook) for maximum flexibility
• Document your workflow for future reference, especially in professional contexts

Remember that email attachment capabilities directly correlate with your email provider’s architecture. Services built on open standards (IMAP/SMTP) generally offer more flexibility than proprietary webmail-only platforms.

If privacy and security are priorities in your email workflow—particularly when attaching sensitive correspondence—consider exploring Onion Mail, which combines Tor anonymity, PGP encryption, and standard email protocols. With no registration data required and full IMAP/SMTP support, you gain both privacy protection and compatibility with powerful desktop clients that make email attachment seamless.