My first thought was to jump into Keyboard Maestro and create a macro that would show you the link you clicked on before anything actually opens the link.
But I couldn’t figure that out…
Then I thought — Applescript? Maybe, but I don’t know how to do that.
Next I thought about a whole system implementation where we create an App in Automator that is set as the default browser, shows you URLs clicked on, and opens the URL if you want. Not only could I not figure this out, but holy shit that sounds like a horrid solution.
So my thought now is rather simple: someone should write a plugin for Mail.app that is a link checker. All it does is shows you a dialog when you click on the link — this dialog exposes the full URL. If you want to open it, hit return, or a button — otherwise you don’t have to open it.
(Also this plugin should fix the flaw in Mail.app whereby Mail will not open links in the background.)
Anyways, if someone wants to build that I would be glad to test it — if it works I’ll promote it (hell everyone should).