What is an MSG file?

An MSG file is a single email message, contact, task or calendar item saved by Microsoft Outlook in its own binary format. This page covers what is inside an MSG file, how to save an email as MSG, how to open one without Outlook and how to turn it into a PDF. SaveMail reads MSG files in your browser; nothing is uploaded.

MSG file: definition and who creates it

An MSG file (extension .msg) is the native way Outlook for Windows stores one item outside the mailbox. For an email it keeps the sender, recipients, date, subject, both the plain-text and HTML body, inline images and the attachments, plus Outlook-specific properties such as categories, flags and the conversation index.

Only Outlook produces MSG files in everyday use: when you drag a message from Outlook to the desktop or a folder, or choose File, Save As with the Outlook Message Format. Some document management and e-discovery systems also write MSG because they are built around Outlook. Gmail, Apple Mail and Thunderbird never create MSG; they create EML files instead.

That is why MSG files so often land with people who do not have Outlook: a colleague drags a message out of Outlook, attaches it, and the recipient on a Mac or a phone sees a file nothing wants to open.

Have the email as a file (EML, MSG, MBOX)? Convert it to PDF in your browser: nothing is uploaded.

How an MSG file is structured

Unlike EML, an MSG file is not text. It is an OLE compound file, the same container format that old .doc and .xls files use: a small file system inside a file, with storages (folders) and streams (files).

Each piece of the message lives in its own property stream, named by a MAPI property code. The subject, the sender's address, the plain body, the HTML body and the received time are separate streams; recipients are stored as numbered sub-storages, and so is each attachment, with its own name, size and bytes. A properties stream at the top level lists which properties exist and their types.

Two consequences follow. A program needs an OLE parser plus a MAPI property table to read an MSG, which is why a text editor shows gibberish. And strings can be stored as Unicode or in an older ANSI code page, so MSG files from old Outlook versions sometimes show wrong characters in simple viewers.

How to save an email as an MSG file

"Save as MSG" is Outlook's phrase for writing one message to disk. The steps in classic Outlook for Windows:

1. Open the message or select it in the list.
2. Choose File, then Save As.
3. Pick a folder, leave the type as Outlook Message Format (Unicode), and press Save.

Faster: drag the message from the Outlook list straight onto the desktop or into a folder; Outlook writes an .msg file named after the subject. Select several messages and drag them together to get one MSG per message. Outlook on the web and the new Outlook for Windows do not offer Save As MSG; their Download or Save option writes an EML file instead. The full picture is in how to save an Outlook email as a file.

How to open an MSG file

With Outlook on Windows, double-clicking an MSG file opens it as a message window, attachments included. Without Outlook, open it in your browser:

1. Open the MSG to PDF converter on SaveMail.
2. Drop the .msg file on the page.
3. Read the headers and body; download attachments singly or as a ZIP.

The MSG is parsed by JavaScript in the tab, so it works on a Mac, on Linux, on ChromeOS and on a phone, and it keeps working offline once the page has loaded. No account is needed. Every alternative, including Outlook for Mac and desktop viewers, is listed in how to open an MSG file.

Converting an MSG file to PDF, and what to expect

After the message opens in SaveMail, press Save as PDF. The browser's print dialog appears; select Save as PDF as the destination. The PDF keeps the header block (From, To, Cc, Date, Subject, Message-ID), the body with inline images, and a list of attachment names and sizes. Text stays selectable, so the PDF can be searched later. Compact mode removes quoted replies and signatures when you want a shorter file.

Limits worth knowing before you start:

• Attachments are not embedded in the PDF; download them from the list and file them alongside it.
• Very large attachments inside an MSG are slow to extract in the browser.
• Encrypted or signed messages (S/MIME) are displayed as encrypted, not decrypted.
• One message is converted at a time; there is no merged PDF of several MSG files.
• Editing the message text and converting a PDF back to MSG are out of scope.

MSG files are typically larger than the same message as EML because of the property overhead, but still small unless they carry big attachments.

MSG vs EML vs MBOX vs PST

If you need to send a single Outlook message to someone outside your organization, EML or PDF travels better than MSG. More on the other formats: MBOX and PST.

Frequently asked questions