I am running into a situation whereby the default application for opening pdfs was changed to PDF-Xchange instead of Adobe and Mail to Outlook 2010, 2016 instead of the built-in default Microsoft Mail app. These changes were made after retrieving the valid hashes for both applications via Reg Queries and then referencing the respective entries in the App-assoc.xml spec file. This worked on all targeted computers with the exception of one that still resets pdf to adobe acrobat anytime the users logs on again. This means he has to always set his preferred default pdf and mailto apps manually which makes it very cumbersome for since he always reset to preferred default app after every log on.

Has anyone experienced this and would like to share some possible troubleshooting tips? I read somewhere that it could be a rogue application behind the scenes forcing this behaviour.


What if we set this via registry? Refer to my settings here


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  • I will go ahead and set via computer startup script for targeted problematic computer using the following commands e.g 'Set-ItemProperty Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Associations\UrlAssociations\mailto\UserChoice -name ProgId Outlook.URL.mailto.14' . Refer to link for details -> pastebin.com/Q5ixDq9W – john zuh Nov 11 '19 at 22:26
  • Does that helps? – Perry Nov 14 '19 at 8:10
  • Works as expected – john zuh Dec 1 '19 at 22:20

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