Add-In Error: Content is blocked because it isn't signed by a valid security certificate in Outlook 365

Question

Currently I am developing my custom add-in for outlook 365/

Then I am trying to use it for testing for example it shows me error. I investigated and found what it opens addon in iframe in edge browser. So question is how to add certificate/s to edge to allow my app to work in it?

I am using :

• Outlook 365 desktop edition

What I tried

• Switching flag in Edge browser to allow not certified certificates to "work"(same thing was done in chrome and it worked there)

• As suggested in comments to use office-addin-dev-certs. Well I installed them on my project by using npm install office-addin-dev-certs and then I am trying to verify it by this command office-addin-dev-certs verify it throws error in console see image 3

• exported certificates from chrome and imported them in edge browser and also on my machine . It did not helped.

Answer 1

The easy solution that worked for me was remove .office-addin-dev-cer from User folder. Then by running my Add-Ins by npm start I got popped by a message box to remove existing certificates (ca.crt, localhost.crt). After clicking on Yes for 3 messages I have been asked to install new certificates and all certificates re-installed and my Add-Ins works fine now.

Answer 2

Well I found the solution. solution was to create and add certificate to app. In desktop outlook aka office outlook for desktop it uses Edge browser as sidebar for Add-ins.

Reason is what browsers need Subject Alternative Name in certificate. So need to create a trusted self-signed SSL cert for localhost (for use with Express/Node) . So the solution was found in this post.

Answer 3

This may be an old issue which has resurfaced. You can see more info here

Answer 4

While not strictly required in all add-in scenarios, using an HTTPS endpoint for your add-in is strongly recommended. Add-ins that are not SSL-secured (HTTPS) generate unsecure content warnings and errors during use. If you plan to run your add-in in Office on the web or publish your add-in to AppSource, it must be SSL-secured. If your add-in accesses external data and services, it should be SSL-secured to protect data in transit. Self-signed certificates can be used for development and testing, so long as the certificate is trusted on the local machine.

See Server requirements for more information.