Recommend me a productivity/workflow tool [closed]
Solution 1:
I believe Things does all that. I use it. I like it.
I don’t know about thunderbird “linking” but with Mail.app it works. You can “drag” a mail onto a task or things to create a new one. Same with documents.
Solution 2:
I think you're looking for OmniFocus, which does (if I recall) everything you want, has a system-wide modal "inbox" tool as well as synchronizable iPad and iPhone apps.
Their price point is ridiculously high in my opinion, but people are fanatical about it.