Formatted emails consist of HTML code. Therefore, the creation of formatted (HTML) emails is the same as the creation of web pages. If you do not have overly high expectations, the built-in editor of BulkMailer should be good to create your emails. This editor offers all the features that are typical to mail clients. For creating professional appealing newsletters you can use a HTML editor of your choice, eg Dreamweaver or MS FrontPage. Load the resulting HTML file via the menu item Email->Load website from file or Email->Load website from URL. To create a beautiful newsletter possibly is a task for your web designer.