Odoo 8 has come with great new features but it removed Compose Message Button without known reason. This causes a lot of difficult when we want to send a single email to one or more recipients without associating the email message with any document in Odoo.
T-Compose Message Button for Odoo 8 has been released as a module to extend the Odoo 8's capability to allow users to open email message composing window anytime and anywhere inside the Odoo software. It is really simple as its name, just a button added which appears as an envelope icon on the top right corner of the Odoo user interface. See its screenshot below: