Integrate Replies with an existing email application like Mailplane

You can use Replies alongside your favorite email application like Mailplane, Mail.app, Sparrow, Postbox, Thunderbird or the Gmail/Google Apps web interface.

Replies uses IMAP to communicate with your email server. You can answer, move, archive conversations in Replies or your normal email application and the changes will automatically be synchronized.

Tip: Check out the 'archive' account settings: Replies can move messages to an archive folder or leave everything in the inbox.