1. Using a web browser, navigate to https://mail.zimbraservice.com and log into the desired mailbox.
2. Select the Mail tab.
3. From within the Mail tab, select the New drop down arrow and choose Message.
4. Above the To: field, click on the Options drop down menu and choose Format as HTML.
Note: Some email clients may not accept messages formatted in HTML. You can set the HTML editor as your default font settings, including style, size and color from the Zimbra Web Client in the Preferences > Composing tab.