Please create a Mavenlink application in https://app.mavenlink.com/oauth/applications/new , and in the line 23 set the client_id to Client ID and client_secret with Client Secret. The callback URL must be http://18.142.0.193/webmail/modules/OAuthIntegratorWebclient/Classes/OAuthClient/login_with_mavenlink.php but make sure it is a secure URL (https://).