Thanks for the comments. We are working on it and keep you posted.
I was Creating a View and noticed that couple of buttons are missing while selecting the fields to display in the View. Please follow the following steps:
1. Click on MassMailer Wizard.
2. Select the Object(Lead/Contact/User) - Step 1 of 5
3. Step 2 of 5 - Specify the Recipients to include.
4. Create a New View/ Edit the existing View.
5. Select Available Fields fields and click on right arrow key to move them to Selected Fields box. Here, I wanted Upward and Downward buttons to shuffle the fields upwards and downwards respectively.