As default, following applications are registered with messaging menu.
HTML Code:
    Chat-> Empathy
    Mail-> Thunderbird
What I want to do is:
HTML Code:
    Chat-> Pidgin
    Mail-> Evolution

If you install evolution (& evolution-indicator) or pidgin it will appear as a seperate menu inside messaging menu.It doesn't register with default menu , even if you uninstall the default applications.

The only way to remove them(default chat & mail menu) is to blacklist them.

A trick that has worked before
After fresh install, If you click messaging menu,there are option like `setup chat` , `set up mail`..etc.

Now before doing anything, if you remove thunderbird & install evolution,then after restart when you first click on `setup mail` it automatically starts evolution setup!! It doesn't create a separate menu named 'evolution`.

Same thing with pidgin. BUT these only works after fresh install.

I think when you first click `setup mail` or `chat` it somehow register the default mail or chat client with `Mail` & `Chat` menu respectively. What I want is to undo these change.

So How do I reset messaging menu to factory default?