Leniy

You can easily send subscription,notification,newsletter,etc by email to your comments users under one post. 
方便给某篇文章的评论用户发送订阅、通知等邮件。
DEMO:<a href="http://blog.leniy.org/mail-to-all.html" title="示例页面" rel="nofollow ugc">Leniy</a> 
<a href="https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=HAENMLDR2UMFJ&lc=US&item_name=Leniy%20Plugins%20Donation&item_number=plugin%2ddonate&currency_code=USD&bn=PP%2dDonationsBF%3abtn_donate_SM%2egif%3aNonHosted" rel="nofollow ugc">Donate link</a>

Mail To All

You can easily send subscription,notification,newsletter,etc by email to your comments users under one post.

INBOX

<h4>Inbox Form WordPress plugin</h4>
The Official Inbox Form plugin makes it easy to grow your newsletter subscriber list from your WordPress blog or website. The plugin automatically integrates your WordPress form with your Inbox email marketing account.
If you don’t have Inbox account yet, <a href="https://useinbox.com/" rel="nofollow ugc">you can signup for a FREE here</a>.
Once you activate the plugin, you’ll be able to select and add any of the pre-built forms from your Inbox account. You can place the form in the sidebar using a widget or use a shortcode to put it wherever you want.
Setup is fast and easy! You just need to enter your Inbox account API Key and you’re all set.
Plugin features include:
<ul>
<li>Easily-to-add inline & popup forms from Inbox to your WordPress blog or website</li>
<li>WordPress 5 new editor support</li>
<li>Place forms using widget or shortcode</li>
<li>Auto place popup forms by rules</li>
</ul>

INBOX Forms

Add newsletter sign up forms to your WordPress site. Subscribers will be saved directly to your Inbox account. Super easy to set up!

Mail To All vs INBOX Forms