Catch and block links that were triggered by an external application like a desktop mail client

Dear mozilla community,

I’m searching for a possibility to catch and block with my firefox extension the loading of a link, which was triggered / opened by an external application. I’ve tried already with multiple API-Hooks:


Sadly I’m not able to catch all links that are coming from external applications. There are still some options when the link wasn’t catched. Also using the API-Calls mentioned above, I’m not able to block the webRequest before it executes. In the background the webRequest was executed before these API-Calls.

What I need:
A hook which catches external link openings, wich blocks the webRequest, does some analytics and decides if it will start the webRequest or block it.

Thank you for your help & greetings,