Not loaded. Certificate of signed and load at startup COM Add-in is not in trusted source list

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Not loaded. Certificate of signed and load at startup COM Add-in is not in trusted source list
What is the trusted source list? 
Inspirometer Developer




Posts: 34
Joined: 2017-10-13
In fixing some of the certificate problems we had earlier we learned that some of our clients machines are not starting the add-in at all. When inspecting the problem in Outlook's add-ins list we see the error "Not loaded. Certificate of signed and load at startup COM Add-in is not in trusted source list".

We have tried the following approaches:

  • Disabling “Apply macro security settings to installed add-ins”. While we know this WOULD work, it cannot work for our clients as the ability to change this is disabled by group policy. Getting this changed is unlikely to happen.
  • Installing our new code-signing certificate into the Trusted Publishers store. I fully expected this to work but there was no change in behaviour.


So no I'm wondering how we resolve this. What is the "trusted source list" if not the Trusted Publishers store?
Posted 18 Oct, 2018 10:09:11 Top
Inspirometer Developer




Posts: 34
Joined: 2017-10-13
This was another "so close yet so far" problem. We eventually realised that while we updated the publishing certificate and installed the certificate on client machines, what we didn't do was update the certificate in Project > Add-in Express > Signing Options therefore the client machines didn't recognise the publisher of adxloader.dll and InspirometerMeetingsToolADX.dll so it was disabled. Adding the correct signature for signing these files fixed the problem.
Posted 19 Oct, 2018 06:33:56 Top
Andrei Smolin


Add-in Express team


Posts: 16223
Joined: 2006-05-11
Thank you for sharing your experience!

Regards from Belarus (GMT+3),

Andrei Smolin
Add-in Express Team Leader
Posted 19 Oct, 2018 06:57:45 Top