Stationery feature of Microsoft Outlook provides a consistent set of design elements such as fonts, bullets, colors, effects, themes and backgrounds that can be applied to your messages. You can also create your own stationery. This option is available only if you use the HTML message format. If you try to apply a stationery when the Text message format is being used, the following message "The themes are not installed "
Apply stationery and themes to your messages:
Click Tools > Options > Mail Format
Next to "Compose in this message format", select "HTML ."