---
title: "Attachment — Glossary — Mbox Viewer"
description: "A file — such as a PDF, image, or spreadsheet — embedded in an email message and encoded as a MIME part, separate from the message body, intended for the recipient to save or open."
url: https://mboxviewerpro.com/glossary/attachment/
language: en
source: Mbox Viewer
---

[Mbox Viewer](https://mboxviewerpro.com/)  [Glossary](https://mboxviewerpro.com/glossary/)  Attachment

# Attachment

A file — such as a PDF, image, or spreadsheet — embedded in an email message and encoded as a MIME part, separate from the message body, intended for the recipient to save or open.

An attachment is a MIME part with a Content-Disposition header set to attachment, optionally including a filename parameter. The part's content is typically encoded with Base64 so that binary data can travel through text-based mail infrastructure. The Content-Type header identifies the file type, such as application/pdf or image/png, so the recipient's mail client knows how to handle it.

Attachments are one of the most common reasons people search their email archives — locating a contract, an invoice, or a photo sent years ago. Filtering by has:attachment narrows results to messages that contain at least one attached file. Additional filters on filename or file type can narrow further, for example finding all messages with a PDF attachment from a specific sender.

Mbox Viewer decodes MIME attachments and provides previews for common file types. It also supports batch export, allowing you to extract all attachments from a set of messages to a folder in one operation — useful when recovering files from a large archive without opening each message individually.

## Related terms

[

MIME

Multipurpose Internet Mail Extensions — the standard that defines how email messages encode non-ASCII text, HTML bodies, attachments, and other binary content within the plain-text structure of email.

](https://mboxviewerpro.com/glossary/mime/)[

Base64

A binary-to-text encoding scheme that represents arbitrary binary data using only 64 printable ASCII characters, widely used in email to safely transmit attachments and binary content.

](https://mboxviewerpro.com/glossary/base64/)[

Inline image

An image embedded directly into an HTML email body using a Content-ID (cid:) reference, rather than attached as a separate downloadable file. The image data is stored as a MIME part within the same message.

](https://mboxviewerpro.com/glossary/inline-image/)

[Back to the full glossary](https://mboxviewerpro.com/glossary/)

## Read your MBOX files on Mac and Windows

[Download on the Mac App Store](https://apps.apple.com/app/mbox-viewer-pro/id6759237715) [Microsoft Store](https://apps.microsoft.com/store/detail/9NW3GVFG7DDB)