Initial Development

How about:

```html
<p class="subscribe-email__response"></p>

<fieldset class="subscribe-email__form">
    <label for="{{ emailName }}">Email Address</label>
    <input class="subscribe-email__input subscribe-email__input--email" type="email" name="{{ emailName }}" required>
</fieldset>

<button class="subscribe-email__button" type="submit">{{ submitText }}</button>
```

 - In HTML5 you don't need to wrap form controls in something anymore, but such containers can still be helpful as a styling hook.

 - Should definitely label the input

 - Buttons are much easier to style because they can take pseudo-elements

 - I'm neutral on ordering the response above/below the form, but it's definitely more conventional to put summary-style messaging like that up top. It sort of works as inline validation-style messaging when there's just a single input as in this case though.