How to Attach an Email: Files, Images, and Forwarded Messages Explained

Attaching something to an email sounds straightforward — and usually it is. But the word "attach" covers more than most people realize. You might be attaching a file, an image, a document, or even an entire email thread. The process varies depending on your email client, device, and what exactly you're trying to send. Here's how it all works.

What "Attaching" Actually Means in Email

When you attach something to an email, you're embedding a file within the message so the recipient can download or view it on their end. Attachments travel alongside the email body as separate data packages. They don't live "inside" the text — they're bundled with the message by your email client and decoded on the receiving end.

Common attachment types include:

• Documents — PDFs, Word files (.docx), spreadsheets (.xlsx), text files
• Images — JPEGs, PNGs, GIFs, screenshots
• Compressed files — ZIP or RAR archives containing multiple files
• Audio and video — MP3s, MP4s (though these come with size caveats)
• Other emails — forwarded messages or saved .eml files

How to Attach a File: The General Process

Most email clients follow the same basic pattern regardless of platform.

On desktop (Gmail, Outlook, Yahoo Mail, Apple Mail):

1. Open a new compose window
2. Look for the paperclip icon — this is the universal symbol for attachments
3. Click it to open your file browser
4. Navigate to and select the file you want to attach
5. Wait for the upload to complete before sending

Some clients also let you drag and drop files directly into the compose window, which is often faster than using the file browser.

On mobile (iOS Mail, Gmail app, Outlook app):

1. Start a new message
2. Tap the paperclip icon, an arrow icon, or look in the formatting toolbar — placement varies by app
3. On iOS, you may be prompted to choose between files, photos, or scanned documents
4. On Android, you'll typically get access to your file manager or gallery

The exact location of the attachment button differs across apps, but every major email client includes one.

Attaching an Email to Another Email 📎

This trips people up. If you want to forward an existing email as an attachment (rather than an inline forward), the process is slightly different.

• Gmail: Open the email, click the three-dot menu, and select "Forward as attachment." This sends the original as an .eml file.
• Outlook (desktop): Drag the email from your inbox directly into a new compose window. It attaches as a message file.
• Apple Mail: Select the email, go to Message > Forward as Attachment.

This is useful when you want to share a full email thread without pasting it inline, or when you need to preserve original headers and metadata.

File Size Limits Matter More Than You'd Think

Every email provider caps how large an attachment can be. These limits exist because email servers weren't designed to transfer large files — they're built for text.

If your file exceeds the limit, you have a few options:

• Use a cloud link instead — upload to Google Drive, Dropbox, or OneDrive and share the link
• Compress the file — ZIP archives can meaningfully reduce file size
• Split the content — send multiple emails with portions of the files

Gmail and Apple Mail both have built-in features that automatically offer cloud-based alternatives when your attachment is too large.

Inline Images vs. True Attachments

There's a distinction worth knowing: inline images appear inside the body of the email, while attached images show up as downloadable files below the message.

When you paste or drag an image directly into the email body, most clients treat it as inline. When you use the paperclip/attachment button to add an image, it typically appears as a traditional attachment. Some clients — especially on mobile — handle this differently, and the recipient's email client may display the same file differently than you expect.

What Affects How Attachments Behave 🖥️

The experience of attaching and receiving files isn't identical for everyone. Several variables shape what actually happens:

• Email client — Web-based clients (Gmail, Yahoo) behave differently from desktop apps (Outlook, Thunderbird) or mobile apps
• File type — Some file types are blocked by email providers or corporate firewalls (executable files like .exe are commonly restricted)
• Recipient's client — A file that looks perfect on your end may display differently in someone else's inbox
• Network speed — Large attachments take longer to upload on slower connections
• Security settings — Corporate or institutional email accounts often have stricter limits or blocked file types

When Attachments Aren't the Right Tool

For very large files, frequent collaboration, or sensitive documents, email attachments aren't always the best fit. Cloud-based file sharing (Google Drive, OneDrive, Dropbox) allows for larger files, version control, and access management that email can't provide. Password-protected files add a layer of security that plain email attachments lack entirely.

Whether attaching a file directly makes sense — versus sharing a link or using a dedicated file transfer tool — depends on how large the file is, how sensitive the content is, and what your recipient is best equipped to receive. Those variables sit entirely within your specific situation and workflow.