Mailplane

App Description
Mailplane is touted as the “best way to use Gmail on your Mac”. It’s designed to give you the power and convenience of Gmail’s web-based web client while also introducing features that can only be delivered through a dedicated app. For example, Mailplane integrates with the Contacts app and can be set to be your default mail application.
You can create an OmniFocus action based on an email by invoking Mailplane’s “Save Clip” feature then choosing “OmniFocus” from the available options. A new action is created with the title of the action matching the subject of the email.
If there is any text selected, this text will automatically be added to the note field of the new OmniFocus action. Otherwise, the entire contents of the email will be added to the note field.
Additionally, two links are automatically added to the note field: one that allows you to access the email from within Mailplane and a second that provides access to the email through Gmail’s standard web interface.