Windows 8.1 Mail app will no longer open attachments

Question

• Windows 8.1
• Mail app (officially "Mail, Calendar and People" app in the Microsoft Store)
• configured with Outlook.com account

User used to be able to click on attachments and they would open in the associated application.

Specifically:

• *.pdf files --> Adobe Reader 11.0.5
• *.docx files --> Microsoft Word 2007
• *.mp3 files --> QuickTime 7 (latest version)

As of 2 days ago, the Mail app will open PDF files, but mp3 and docx files results in the following message appearing in the Mail app above the attachment(s):

We can't open this file. Do you want to save it and try opening it with another app?

The user can save the files, browse for them and open them successfully.

Also, right-clicking the attachment provides 2 options in a drop-down list:

• Save
• Open With

If you click "Open With", the list simply disappears and nothing happens.

Troubleshooting Steps

• I repaired Office and QuickTime. No change
• I associated mp3 files with Windows Media Player. The icon in the Mail app changed from a QuickTime logo to a Windows Media Player icon, but would not open from within Mail. No change
• I ran the Microsoft App Troubleshooter. No change

I searched for this exact error and see people have been having a similar experience since 2012. Surely there's a solution. It was working fine and works on other computers.

Answer 1

Uninstalling the app and re-installing the app from the store did not work.

Running through logs, temporary file directories, default file and program associations, I kept coming across various "FF" entries that struck me as odd or out of place. After a week or more of troubleshooting to no avail, the user sheepishly confessed they had previously installed a free file opener called FF something (I think it was called Free File Opener?) and then uninstalled it before contacting me (why do users always leave out the most important information!?).

It basically hijacks hundreds of file associations on the computer. The only way to fix it, was to hunt down the FF app, re-install it, use it to reset everything back to default, and then uninstall it. After doing this, the attachments started opening properly.