After some heavy googling, I've concluded that I'm unable to locate information on the id names for the different components of the ribbon in Office.
For instance, even though the following XML works, I need to hide the add-in error display due to TabMail being at fault when a new email is being created. It's my understand that it's because I currently target all windows in Outlook but should be only targeting the main one. When a new email is being created, my add-in tries to insert itself in there too failing and complaining.
<ribbon>
<tabs>
<tab idMso="TabMail">
<group id="Animals" label="Animal group">
<splitButton id="MainSplitButton" size="large">
<button id="Donkey"
label="Donkey me"
getImage="GetImage"
showImage="true"
onAction="Donkey_Click"/>
...
While preferring the digital information, I'd be willing to purchase some literature covering Office add-in development. Even on that subject my search was inconclusive (many hits, no one of which feeling like the right stuff.)
For Office 2007 see this link, for Office 2010 Fluent UI click here and the 2013 version is here.
I also didn't find much good literature, but there is tons of posts on forums and since I work for Excel only (which has quite a good developer community) I settled with that.