unity-mail binary package in Ubuntu Bionic i386

 Unity Mail is an application that integrates your mail into the Unity,
 MATE, Xfce, LXDE and other environments.
 .
 It displays notifications about incoming mail, shows the number of unread
 messages and displays subjects in the Messaging Menu.
 .
 The Launcher item also has a quicklist that provides quick access to your
 mail folders (configured for GMail by default). It also allows you to quickly
 compose a new message.
 .
 Unity Mail starts automatically, all you have to do is to enter your accounts
 settings in a configuration dialog.

Source package