If you mean that your email style is "use default style", then it'll use whatever style you use by default on the forum. Unfortunately, different email clients support different things, so you may need to do some testing with this. You can make some style-specific email changes via the "Emails" style property group. If that doesn't do enough (and it may not as it looks like your text is white but the BG color isn't coming through), you can create a new style specifically for the emails and assign that as your email style.