[orca-list] swapping evolution for thunderbird

[Michael Weaver <weavermicha googlemail com>]

I have the latest version of Ubuntu Mate installed but it comes with 
Evolution which seems to be inaccessible with Orca or at least 
navigating to messages is.

I have managed to get Thunderbird but can only run it from a terminal by 
typing Thunderbird.

How do I get the version or update the version where I will see it on 
the desktop rather than me having to type alt F2, mate-terminal and then 
type thunderbird?