You can compose your messages using HTML as the rich-text editor. Messages created using HTML can have text formatting, numbering, bullets, coloured background, tables, and links which can make messages easy to read and visual content such as pictures.
Some email clients may not accept messages formatted in HTML, (these will use plain text and any HTML content may be displayed as gibberish containing nonsensical characters).
You can set the HTML editor as your default editor and set the default font settings, including style, size and colour from the Web Client the Preferences -> Composing tab.
Webmail Lite Example
Webmail Plus Example
The Font, Size and Colour options can be selected by the appropriate drop-down box - see images.
Selecting As Text will compose an email in Plain Text.
This option is not available for Webmail Mobile, and all emails are sent in Plain Text.