As you may know, Dekko is an open-source email client developed for Ubuntu Touch by one of the community members. For now, it is still a beta application and does not run flawless, but it has the basic features of a modern email client.
I have managed to install Dekko 0.5.7 Beta (the latest version available, so far) on Xubuntu 15.04 Vivid Vervet.
To install Dekko on Ubuntu 15.10 Wily Werewolf and Ubuntu 15.04 Vivid Vervet you just need to add the PPA to your system, update the local repository index and install the dekko package:
$ sudo add-apt-repository ppa:ubuntu-touch-coreapps-drivers/daily
$ sudo apt-get update
$ sudo apt-get install dekko
Optional, to remove dekko, do:
$ sudo apt-get remove dekko