Pluton theme comes with simple storage email addresses of subscriptions to a newsletter in .txt file with PHP script.
If you already have a MailChimp account, maybe you want to use the Mailchimp signup form with the Pluton theme. Normally, MailChimp uses an embedded HTML form to collect email signups for your newsletter campaigns. You can use this customized snippet for this:
<form action="FORM_ACTION_URL" method="post" id="mc-embedded-subscribe-form" name="mc-embedded-subscribe-form" class="validate inline-form" target="_blank" novalidate>
<input type="email" value="" name="EMAIL" placeholder="Enter your email" class="span8 required email" id="mce-EMAIL">
<button type="submit" name="subscribe" id="mc-embedded-subscribe"class="button button-sp">Subscribe</button>
<div style="position: absolute; left: -5000px;">
<input type="text" name="BOT_PREVENTION" tabindex="-1" value="">
</div>
</div>
</form>
*Replace FORM_ACTION_URL and BOT_PREVENTION with your own. To get these fields you must generate embedded signup form in your Mailchimp dashboard.