What is the crowd's opinion of eSputnik?

From 3.5 billion comments

I used https://esputnik.com/ like in this post.

Also I used this script via google tag managet to send events to service

<script>

function sendEventForToken(pushToken) {

es('sendEvent', 'name_of_event', pushToken);

}

es('getPushToken', sendEventForToken);

</script>

You may want to do a domain spam check and file an appeal with Google support with some test emails. If your domain is a G Suite/Google Apps account, the domain administrator usually has access to  24/7/365 support from Google - see this page

The best Email Service Provider:

• <strong>Bullmailer.com</strong> - Easily Create, Send & Analyze Emails. Reach the Inbox. 100% Delivery with Amazon SES
• <strong>Bulkresponse</strong> - Send 50k Emails In 30 USD only.
• Infodataplace .com
• Emaildatabase .marketing
• eSputnik.com — Marketing Automation Software for B2C