If you want to set a custom email icon for your team members, With the following custom code, you can do it easily. If you check the code, you will see that there is a filter hook (sp_team_pro_member_email_icon) available through which you can customize the icon. You just need to copy and paste the HTML code of the custom icon from Font Awesome (version 4) into the code.
function sp_team_pro_member_email_custom_icon(){
return '<i class="fa fa-envelope-open"></i>';
}
add_filter( 'sp_team_pro_member_email_icon', 'sp_team_pro_member_email_custom_icon' );