A customer may have a requirement to change the default font for the email editor (FCKeditor). By default, the email editor will default to Times New Roman.
This can be modified for each user theme. The default font for the text editor is set in \CRM\WWWRoot\Themes\FCKeditor\theme name\css\fck_editorarea.css
font-family: Times New Roman;
Sans-serif fonts are recommended for on-screen use. The following font settings will provide good ClearType support on clients where this is supported, as well as failover for other systems:
font-family: Calibri, Verdana, Arial, Helvetica, sans-serif;