Working on a custom theme but want to use the standard newsletter signup. This seems to be fairly generically used across Shopify's own and other themes.
{% form 'customer' %}
{{ form.errors | default_errors }}
<input type="hidden" name="contact[tags]" value="newsletter">
<div class="input-group">
<input type="email" value="" placeholder="" name="contact[email]" id="NewsletterEmail" autocorrect="off" autocapitalize="off">
<div class="input-group__btn">
<button type="submit" class="btn" name="commit" id="Subscribe">go</button>
</div>
</div>
{% endform %}
However, if you try to add an email address, CAPTCHA appears with a second submit button which then attempts to hit /contact which 404's - and the email is not captured in the customer list.
