How to uninstall cairo-dock-mail-plugin from Ubuntu
To uninstall just cairo-dock-mail-plugin package itself from Ubuntu execute on terminal:
sudo apt-get remove cairo-dock-mail-plugin
Uninstall cairo-dock-mail-plugin and it's dependent packages
To uninstall the cairo-dock-mail-plugin package and any other dependant package which are no longer needed on Ubuntu.
sudo apt-get autoremove cairo-dock-mail-plugin
If you also want to delete configuration and/or data files of cairo-dock-mail-plugin from Ubuntu then this will work:
sudo apt-get purge cairo-dock-mail-plugin
To delete configuration and/or data files of cairo-dock-mail-plugin and it's dependencies from Ubuntu then execute:
sudo apt-get autoremove --purge cairo-dock-mail-plugin
cairo-dock-mail-plugin package information
Cairo-dock - Mail plug-in
A collection of official plug-ins and applets for cairo-dock. This plug-in is very useful to warn you when you get new e-mails. This can check in any kind of mailbox (yahoo, gmail, etc).
More information about apt-get remove
Advanced Package Tool, or APT, is a free software user interface that works with core libraries to handle the installation and removal of software on Debian, Ubuntu and other Linux distributions. APT simplifies the process of managing software on Unix-like computer systems by automating the retrieval, configuration and installation of software packages, either from precompiled files or by compiling source code.
apt-get is the command-line tool for handling packages, and may be considered the user's "back-end" to other tools using the APT library.
apt-get remove is identical to install except that packages are removed instead of installed. Note that removing a package leaves its configuration files on the system. If a plus sign is appended to the package name (with no intervening space), the identified package will be installed instead of removed.