@mabeleira: Of course you should use Libre Office and Thunderbird. But there is not really a cloud based alternative. (for those that want to jump on the cloud hype because 'advisors' are hammering to fill their pockets and not to give the best solution)
However, I recently read news that libreoffice can be run from the cloud with owncloud as data provider: https://www.collaboraoffice.com/code/
You can check out the code of CODE at http://cgit.freedesktop.org/libreoffice/online/
Alternatively you can look at rollapp: https://www.rollapp.com/apps But this has the same problem as office365 and google apps: your are not in control of your data.
You could try fernapp to go by this problem, but it is not scalable: http://www.fernapp.com/ I have tested this a few years ago, but it was very buggy, and it looks like development has stalled a bit.. 