Someone sends you an email with an attachment that ends in .msg, or you go back to one you filed away on the shared drive, and it will not open. Sometimes nothing happens at all. Sometimes Windows asks which program to use. Sometimes you get an error saying the file cannot be found, or that Outlook has already started.

A .msg file is a single email saved out of Outlook as a file of its own, with the sender, the date, the message and any attachments all bundled together. Only Outlook can open one properly, which is why these files are more fragile than a PDF.

Try this first

1. Open Outlook first and leave it running. Then go back and double-click the .msg file. A .msg file cannot open on its own, it needs Outlook already awake to open inside. This one fixes it more often than anything else on the list.
2. Tell Windows which program to use. Right-click the file, choose Open with, and pick Outlook. If Outlook is not listed, choose Choose another app and look for it there. Once it opens, you can tick the box to always use Outlook for these files.
3. Unblock the file. Files that arrive by email or download are often held back by Windows as a precaution. Right-click the file, choose Properties, and look at the bottom of the General tab. If there is an Unblock tick box, tick it, click OK, and try again.
4. Copy it somewhere local. If the file is sitting on a network drive, in OneDrive or still inside a zip folder, drag a copy to your desktop and open that. Files opened from inside a zip in particular tend to fail.
5. Check the size and the name. Right-click and choose Properties. If the file is 0 KB or only a few kilobytes, there is nothing in it to open and it needs to be sent again. Also check the name still ends in .msg. A file renamed along the way, or saved as .eml by a different mail program, will not behave.

If that didn't fix it

If the file opens fine for the person who sent it but not for you, the problem is on your computer rather than in the file. The usual culprit is more than one version of Office installed at the same time, each arguing over which one owns .msg files.

You can check this safely without changing anything. Click Start, open Settings, then Apps, then Installed apps. Type office into the search box. Look for more than one entry along the lines of Microsoft 365 Apps, Microsoft Office, or an older year such as Office 2016.

Please do not uninstall either of them. Send us a screenshot of that list instead. Removing the wrong one takes your mail offline, and getting it back can mean rebuilding your Outlook profile, re-downloading years of email and sorting out the licence. It is a fifteen-minute job for us and a very long afternoon for you. Log it with us and we will sort out which one goes.

When you log the ticket, it helps to include the screenshot of the Office entries, the exact wording of the error, the size of the file, and whether every .msg file fails or just this one.

Why this happens

• Two versions of Office. Windows can only point .msg files at one program, and when two versions are installed the pointer often lands on the one that is not properly set up.
• The file association drifted. Another program that handles email, or a Windows update, can quietly claim .msg files for itself.
• The file was damaged in transit. Some mail filters and security gateways strip or truncate .msg attachments because they can carry other files inside them. What lands in your inbox is then only part of the original.
• The file was renamed. Dropping or changing the ending, even by accident when saving, leaves Windows with no idea what to do with it.

How to avoid the problem next time

If you only need someone to read an email rather than keep it as a file, forwarding it is far more reliable than saving it as a .msg and attaching that. If you do need to send a .msg, putting it in a zip folder first stops most mail filters from interfering with it on the way.

Still stuck?

Log a ticket at portal.yougrowit.com.au or email support@yougrowit.com.au. If it is stopping you working right now, call 03 9028 4358.

Support hours are Monday to Friday, 8:30am to 5:30pm Melbourne time, excluding Victorian public holidays.