Classic Outlook to New Outlook: MSG Files – Open saved messages without Classic Outlook

When you switch from Classic Outlook to the new Outlook for Windows, saved MSG files from old emails no longer open by double-clicking. This happens because the new Outlook does not register itself as the default handler for the MSG file format. This article explains exactly why MSG files fail to open in the new Outlook and provides three reliable methods to open saved messages without needing Classic Outlook installed.

The MSG format is a proprietary file type created by Classic Outlook to store individual email messages, contacts, and appointments. The new Outlook does not natively support opening MSG files directly. You will learn how to use a free viewer, convert MSG files to the EML format, or restore the file association to open them in the new Outlook.

Why MSG Files Do Not Open in the New Outlook

The MSG file format is a proprietary Microsoft format tied to Classic Outlook (the Win32 desktop version). When you save an email from Classic Outlook, it creates an .msg file containing the message body, attachments, headers, and metadata. The new Outlook for Windows, built on a different codebase, does not include the necessary handlers to parse MSG files.

When you double-click an MSG file after installing the new Outlook, Windows may show an error stating that the file type is not associated with any program, or it may try to open Classic Outlook, which may not be installed. The core issue is that the new Outlook registers itself only for EML and OFT file types, not for MSG.

Three Methods to Open MSG Files Without Classic Outlook

Method 1: Use a Free MSG Viewer Application

1. Download and install a free MSG viewer
   Go to the Encryptomatic website and download the Free MSG Viewer application. Run the installer. This viewer reads MSG files without requiring Outlook or any email client.
2. Open the MSG file in the viewer
   Launch the MSG Viewer. Click File > Open or drag your .msg file into the application window. The message content, including the body, sender, recipients, and attachments, appears in a readable format.
3. Print or export the message
   Use File > Print to create a paper or PDF copy. To save the message in a different format, click File > Save As and choose EML or TXT. EML files open natively in the new Outlook.

Method 2: Convert MSG Files to EML Format

1. Use a dedicated MSG to EML converter
   Download a free tool such as SysTools MSG to EML Converter or the built-in conversion option in the Free MSG Viewer. These tools convert .msg files to .eml without altering the message content.
2. Select the MSG files to convert
   In the converter, click Add Files or Add Folder to select your saved .msg files. Most converters support batch conversion for multiple files.
3. Choose EML as the output format
   Under Output Format, select EML. Set the destination folder where the converted files will be saved. Click Convert or Start.
4. Open the EML file in the new Outlook
   Navigate to the output folder and double-click any .eml file. The new Outlook opens the message in a reading pane. You can forward, reply, or save the message to a folder.

Method 3: Change File Association to Open MSG in the New Outlook

1. Open Windows Settings
   Press Windows + I to open Settings. Go to Apps > Default apps.
2. Search for the MSG file type
   In the search box under “Set defaults for applications,” type .msg. Windows shows the current default app for MSG files, which is likely blank or set to Classic Outlook.
3. Change the default app to the new Outlook
   Click the current app icon or the Choose a default link. A list of installed apps appears. Select Outlook (new) from the list. If Outlook (new) is not listed, click Look for an app in the Microsoft Store and install the new Outlook if missing.
4. Test the file association
   Double-click any .msg file. The new Outlook should now launch and attempt to open the file. Note that the new Outlook may still show an error for some MSG files that use complex formatting or embedded objects.

If MSG Files Still Do Not Open After Changing the Association

MSG file opens as a blank message in the new Outlook

This occurs when the file association change succeeds but the new Outlook cannot parse the internal structure of the MSG file. Convert the file to EML using a dedicated converter and then open it in the new Outlook. EML files use a simpler structure that the new Outlook reads reliably.

MSG file contains attachments that do not appear

The new Outlook may strip or hide attachments when opening an MSG file through the association method. Use the Free MSG Viewer or an MSG to EML converter to preserve all attachments. After conversion, the EML file displays attachments in the attachment bar.

You receive a “File cannot be opened” error

This error typically means the MSG file is corrupted or was created by a very old version of Classic Outlook. Try opening the file in a text editor like Notepad to verify it contains readable text. If the file is corrupted, recovery is unlikely. For older MSG files, use the Free MSG Viewer which supports legacy formats.

MSG vs EML: Key Differences for Opening Saved Messages

Item	MSG	EML
File format	Proprietary Microsoft Compound Document	Standard MIME (RFC 2822)
Native support in new Outlook	Not supported	Fully supported
Opens in Classic Outlook	Yes	Yes
Opens in third-party clients	Limited (requires viewer or converter)	Widely supported (Thunderbird, Apple Mail, Gmail)
Attachment preservation	Embedded in binary structure	Base64 encoded, easily extractable
File size	Larger due to binary overhead	Smaller, plain text based

After reading this article, you can open any saved MSG file without Classic Outlook by using a free viewer, converting to EML, or changing the file association. For ongoing use, convert your important MSG files to EML format to ensure compatibility with the new Outlook and other email clients. As an advanced tip, set up a folder action in the new Outlook to automatically convert incoming MSG attachments to EML using a third-party add-in.