How to Attach an Email to an Email in 2026

Sometimes forwarding just doesn’t cut it. Maybe you need to share an entire email thread with a colleague, or send a specific message as evidence. Whatever the reason, attaching an email to another email is often the cleanest way to share a conversation.

In this guide, you’ll learn:

• How to attach an email in Gmail (desktop and mobile)
• How to attach an email in Outlook (desktop and web)
• How to do it in Apple Mail, Thunderbird, Proton Mail, and Mailfence
• Privacy risks to watch out for when attaching emails
• When attaching beats forwarding

Let’s get into it.

What does it mean to attach an email to an email?

When you attach an email to another email, the original message arrives as a downloadable .eml file. Think of it like a PDF or a photo – except it’s an entire email, complete with headers, formatting, and any original attachments.

This is different from forwarding. A forwarded email gets pasted directly into the body of your new message.

An attached email stays as a separate file the recipient can open on their own. That’s a big deal when you want to preserve the original message exactly as it was.

How to attach an email in Gmail

Gmail makes it fairly easy to send an email as an attachment, but the method depends on whether you’re on desktop or mobile.

On desktop (web browser)

Method 1: Forward as attachment

1. Open your Gmail inbox
2. Select the email(s) you want to attach by checking the box next to each one
3. Click the three-dot menu at the top and choose Forward as attachment
4. Gmail creates a new draft with the selected emails attached as .eml files
5. Add your recipient, write your message, and hit Send

Method 2: Drag and drop

1. Open the email you want to reply to and click Reply
2. Click the pop-out icon in the top-right corner of the reply window
3. Go back to your inbox and find the email you want to attach
4. Drag it from the inbox directly into the pop-out compose window
5. The email appears as a .eml attachment. Then hit Send

Both methods work well. The drag-and-drop approach is great for quick replies, while “Forward as attachment” is better when you’re sending multiple emails at once.

On mobile (iOS and Android)

Unfortunately, the Gmail mobile app doesn’t let you attach one email to another directly. But there’s a workaround:

1. Open the email you want to attach
2. Tap the three-dot menu and select Print
3. Choose Save as PDF instead of a printer
4. Save the PDF to your device
5. Compose a new email and tap the paperclip icon to attach the saved PDF

It’s not perfect (you’ll lose the .eml format), but it gets the job done when you’re away from your computer.

How to attach an email in Outlook

Outlook gives you several options depending on whether you’re using the desktop app or the web version. Here’s how to send an email as an attachment in both.

Outlook desktop app

Method 1: Forward as attachment

1. Select the email you want to attach (don’t open it, just click once)
2. Click the three-dot menu next to the Reply/Forward buttons
3. Choose Other reply actions > Forward as attachment
4. A new email draft opens with the original message attached as a .eml file
5. Add your recipient and send

Method 2: Drag and drop

1. Click New Email to open a compose window
2. Navigate to the folder containing the email you want to attach
3. Click and drag the email into the body of your new message
4. It appears as an attached .eml file

Method 3: Copy and paste

1. Find the email in your inbox
2. Right-click it and select Copy
3. Open a new email, right-click the message body, and select Paste
4. The email shows up as an attachment

Outlook web app

In Outlook on the web, drag and drop is your best bet. 

1. Open a new message
2. Drag any email from your message list into the compose window. You’ll see a “Drop messages here” hint appear.
3. Alternatively, click the three-dot menu on any email and select Other reply actions > Forward as attachment.

Keep in mind that Outlook has a 20 MB attachment size limit. Anything larger will need to go through OneDrive.

How to attach an email in Apple Mail

Apple Mail has a clean built-in option for this on Mac. On iPhone, it takes a bit more finesse.

On Mac

1. Open Apple Mail and start composing a new message (or reply to one)
2. With both the inbox and the compose window visible, drag the email you want to attach into the compose window
3. It attaches automatically in its original format

You can also select any email and go to Message > Forward as Attachment from the menu bar.

On iPhone

On iOS, you can drag and drop, but it requires a two-finger technique:

1. Open the Mail app and start a new message
2. Pull down the compose sheet to minimise it
3. Press and hold the email you want to attach, then start dragging
4. With another finger, tap the minimised compose sheet
5. Drop the email into the message

It’s a bit tricky at first, but once you get the hang of it, it’s quick.

How to attach an email in Thunderbird

Thunderbird handles email attachments a little differently from other clients.

1. Select the email(s) you want to attach in your inbox
2. Right-click and choose Forward as Attachments
3. Thunderbird creates a new message with all selected emails attached

How to attach an email in Proton Mail

Proton Mail is a popular choice for privacy-conscious users. However, it doesn’t have a built-in “forward as attachment” feature in the web app.

Here’s what you can do instead:

1. Open the email you want to attach in Proton Mail
2. Click the three-dot (More) menu below the sender details
3. Select Export
4. The email saves to your device as a .eml file
5. Compose a new message and click the Attachments button to attach the saved .eml file

If you need to do this often, consider using Proton Mail Bridge (available on paid plans). Bridge connects Proton Mail to desktop clients like Thunderbird or Outlook, where “forward as attachment” is natively supported.

Proton Mail has a 25 MB limit for outgoing attachments. The good news? Your exported .eml files are decrypted locally, so recipients can open them in any email client.

How to attach an email in Mailfence

Mailfence makes this easier than most privacy-focused email services, especially if you connect it to a desktop email client.

Mailfence’s web interface forwards messages inline by default, but you can still send an email as an attachment by using a desktop client (like Thunderbird or Outlook) connected via IMAP. Once your Mailfence account is set up in the client, use the same drag-and-drop or “forward as attachment” options described earlier under “Thunderbird” to attach messages as .eml files.

The best part? Mailfence supports sending end-to-end encrypted messages with OpenPGP. If you enable encryption for the message containing your attached .eml file, both the new message and the attachment can be protected in transit.

What about privacy when attaching emails?

If you care about your data, it’s worth thinking about what happens when you attach an email to another email. 

Metadata travels with your attachment

When you attach an email as a .eml file, the full message headers come along for the ride. That includes IP addresses, server routing paths, timestamps, and email client details.

This is actually useful if you’re reporting phishing or need a forensic trail. But it also means you’re sharing more information than you might expect with the recipient.

Mainstream services can read your attachments

Gmail and Outlook encrypt emails in transit using TLS. But once those emails land on their servers, they’re stored in a way the service can access.

That means your attached .eml files sit in both the sender’s and recipient’s accounts, potentially scanned for advertising or accessible to government requests.

Encrypted email changes the equation

With a privacy-focused service like Mailfence, things work differently. End-to-end encrypted emails can’t be read by anyone except you and your recipient – not even Mailfence itself.

If you frequently share sensitive emails as attachments (think legal correspondence, financial records, or HR documents), encryption isn’t optional. It’s the only way to make sure attached emails stay private after you hit send.

For more on protecting your email communications, check out Mailfence’s email security tips.

Strip metadata before sharing sensitive documents

If you’re attaching an email that contains document attachments (like PDFs or Word files), those documents may carry hidden metadata. This can include author names, revision history, GPS coordinates from images, and more.

Before sharing sensitive documents, strip the metadata first. Most operating systems have built-in tools for this (right-click > Properties > Remove Personal Information on Windows, for example).

How to download an email (and attach it manually)

Sometimes none of the built-in methods work for your situation. In those cases, you can download an email first and then attach it to a new message manually.

In Gmail:

1. Open the email
2. Click the three-dot menu
3. Select Download message
4. This saves a .eml file to your computer

In Outlook:

1. Open the email
2. Go to File > Save As
3. Choose a location and save as an Outlook Message Format (.msg) or .eml

In Apple Mail: 

1. Open the email 
2. Go to File > Save As 
3. Save it as a .eml file

In Thunderbird: 

1. Right-click the email in your inbox 
2. Choose Save As to download it as an .eml file.

In Proton Mail: 

Use the Export option described earlier in this guide.

In Mailfence:

1. Open the email 
2. Right-click on the message (left panel)
3. Select Archive > Download
4. The email saves as an .eml file to your computer

Once you’ve downloaded the email, you can attach it to a new message just like any other file. Click the paperclip icon and select the saved file.

This manual approach is also handy if you need to keep your emails secure and want to verify the content before sharing.

Why attach an email instead of forwarding it?

You might be wondering, why bother attaching when you can just forward? There are a few good reasons.

Attaching preserves the full original message. Headers, timestamps, formatting, and any attachments all stay intact. This matters for legal documentation, HR records, or reporting phishing attempts. With the most common malicious attachment types being ZIP archives (62%), DOCM/DOCX files (16%), HTML files (12%), and XLSX spreadsheets (10%), having the original message intact gives IT teams and investigators exactly what they need to trace and verify the threat (Bright Defense Phishing Statistics Report, 2025).

You can send multiple emails in a single message. Instead of forwarding five separate emails, attach them all to one message. Your recipient gets everything in one place.

It keeps things organised. A forwarded email gets mixed into the body of your new message, which can get messy fast. An attached email stays neatly contained as a separate file. This is especially helpful if you follow good email reply etiquette.

Quick comparison: forwarding vs. attaching emails

	Forwarding	Attaching
Original formatting	Partially preserved	Fully preserved
Headers and metadata	Often stripped	Kept intact
Multiple emails	One forward per email	Multiple attachments per email
File format	Inline text	.eml or .msg file
Best for	Quick sharing	Documentation, evidence, bulk sharing

Final thoughts on attaching an email to an email

Attaching an email to another email is one of those skills that saves serious time once you know how. Whether you’re in Gmail, Outlook, Apple Mail, Proton Mail, or Mailfence, the steps are straightforward.

But here’s the thing most people miss: where you send email matters as much as how you send it. Mainstream services store your attachments in plain text on their servers. A privacy-first service like Mailfence gives you end-to-end encryption, built-in document storage, and Mailfence’s full productivity suite, so your emails and their attachments stay private.