Good Afternoon Carley,
The best way to send out formatted HTML mailings to your clients that include Maximizer Merge Fields is to do so using the Campaign Manager.
You can create a Template in HTML using MS Frontpage or some other editor tool (or just notepad if you are comfy with HTML code) and embedd merge fields in the e-mail, then when the campaign runs the fields will be merged and your customers will be sent a very nice looking personalised HTML e-mail.
You can also use the click tracker to record how many people have opened the e-mail.