What is MSG and What does It Store?
MSG is the file format Outlook uses to save one item to disk. Most items are emails. Contacts, appointments and tasks fit too.
The file stores the sender, recipients, subject, date, body and attachments together. Outlook creates the file when you drag a message to a folder or use Save As.
| Detail | MSG |
|---|---|
| Extension | .msg |
| Maker | Microsoft |
| Holds | One email, contact, appointment or task |
| Built on | Compound File Binary format, version 3 |
| MIME type | application/vnd.ms-outlook (not registered with IANA) |
| File kind | Binary, so Notepad cannot show it |
How does Outlook Build the MSG Format?
Microsoft documents the MSG file format in the MS-OXMSG specification. The file works like a small file system with storage and stream objects inside.
- Properties. A stream holds MAPI properties like sender, subject and dates.
- Recipients. A separate storage lists the recipients.
- Attachments. Attachment storages store files and embedded messages.
- Named properties. A mapping storage links custom property names.
Any program that uses MAPI can read this layout, which is why many viewers support MSG.
Do You Know? Outlook 2003 introduced the MSG format as people know it today. The Library of Congress lists the format as fully documented but proprietary.
How do You Open an MSG File?
Method #1: Open in Outlook (Free With Outlook)
Who it suits. Windows users with Outlook installed. Extra application. None.
- Double click the message file in File Explorer.
- Outlook opens the message in its own window.
- Select Reply or Forward if you need to answer it.
New Outlook opens them by drag and drop, right click or double click. Microsoft states that an account needs a qualifying Microsoft 365 subscription to open MSG and OFT files in new Outlook.
Method #2: Open Without Outlook (Free Viewers)
Who it suits. Users with no Outlook license. Extra application. An MSG viewer.
A text editor shows broken characters, because MSG is binary. Use an MSG viewer or a converter instead.
The open MSG files without Outlook thread and the read MSG file without Outlook thread list working options.
Method #3: Fix an MSG File That will Not Open
Who it suits. Users who see an error on double click. Extra application. None.
Check the default app for .msg in Windows settings. Then follow the MSG file not opening in Outlook guide for repair steps.
How do You Save an Email as MSG?
Save as in Classic Outlook (Free)
Who it suits. Users who need one email as a file. Extra application. None.
- Open the message in its own window.
- Select File and then Save As.
- Choose a folder and type a file name.
- Select Outlook Message Format - Unicode (.msg) in the Save as type list.
- Select Save.
Drag and drop works too. Select messages and drop them in a folder. Classic Outlook saves every message as an MSG file.
Heads Up. Microsoft community answers say new Outlook saves EML only. Check your build and switch to classic Outlook for MSG.
Can You Edit MSG Content?
Yes, in Outlook. Open the message, select Actions on the Message tab and choose Edit Message. Then edit the subject or the body text and press Ctrl+S.
Recipients and dates need another route. Convert the message to EML, edit the header lines in a text editor and convert it back.
How do You Convert MSG Messages?
Choose the target first. Every target has its own guide on this site.
- Convert MSG to EML on Mac for open standard files
- Convert multiple MSG files to PST for Outlook data files
- Batch convert Outlook MSG to PDF for sharing
- Extract attachments from MSG files when you need only the files
- Import MSG files to Outlook for mailbox use
Test a few files first and compare the converted messages with the originals.
Frequently Asked Questions
What is an MSG File?
MSG is the Outlook format for one saved item. Items include emails, contacts, appointments and tasks. The file holds the body, the details and attachments.
Can You Open MSG Without Outlook?
Yes. Use an MSG viewer or a converter. A text editor cannot show the content, because MSG is binary.
Is MSG the Same as EML?
No. MSG is a Microsoft binary format for Outlook. EML is an open plain text format that many mail programs open.
Are Attachments Stored Inside MSG?
Yes. Attachments sit inside the file. Open the message in Outlook to save them or use an extractor.
Can You Save Emails as MSG in New Outlook?
Not reliably. Microsoft community answers say new Outlook saves EML files only. Use classic Outlook for MSG.
Which Outlook Versions Create MSG?
Outlook 2003 and later create them. Exchange Server 2003 to 2016 work with the format.
How do You Open Many MSG Messages at Once?
Convert them in a batch to PDF, EML or PST. Then open the converted files in a viewer or in Outlook.
Author's Verdict
MSG preserves Outlook details better than any other single email format, so it suits Outlook to Outlook storage.
Use EML or PDF when you share files with people who do not use Outlook.
Key Takeaways
- MSG stores one Outlook item in a binary file.
- Classic Outlook saves MSG with Save As or drag and drop.
- New Outlook has limits, so check the Microsoft page.