Geary is an IMAP mail client for GNOME 3. It allows you to read and send email with a simple, modern interface. You can install Geary by adding the Yorba team PPA to your systems software sources.
To add the Yorba team PPA and install Geary open a terminal window (press Ctrl+Alt+T) and copy+paste the following lines:
sudo add-apt-repository ppa:yorba/ppa -y
sudo apt update && sudo apt install geary -y
When Geary is installed you can close the terminal window. To start Geary press the SuperKey and type: geary