Sending an email in HTML format could be at risk because is not sure that all the recipient are able to read our newsletter. Some mail clients can’t interpret the HTML format or mark it like Spam. That’s why your have to follow some guidelines. For first tip, I will suggest using a "standard" template. There’s no standard while most used email clients have a poor support to rich-text format, but my meaning was for tested templates.
Manila – A professional looking WordPress theme that features widget-ready and xhtml compliant 3-column layout. The dark pink color in the header adds a bit of eroticism to this professional template. 🙂 The designer and sponsor links in the footer are protected under Creative Commons (Attribution-ShareAlike 3.0), so you must not remove them.
3-column WordPress theme with Web 2.0 looks. This widget ready theme is designed by headsetoptions.org and MandarinMusing. The design (css and images) of this theme is released under Creative Commons (Attribution-ShareAlike 2.5), so the footer links must not be removed. The theme info can also be found at themes.wordpress.net.