Inboxer is an unofficial, desktop application for handling Gmail account. It was made available for free (open-source license). The tool offers all the features of Gmail, so you can receive and send messages, save working copies, delete unnecessary emails and use your contact list.

You'll also find a built-in search engine and various settings to customize labels, signatures, templates, keyboard shortcuts and many other options. Inboxer also allows you to add your own reminders at the top of your inbox, store emails and reminders so that they are displayed in the Received at a given moment (e.g. next week), and also offers features for grouping messages that can be assigned to specific categories (shopping, finance, travel, etc.).