"Email marketing software that drives sales. Create, send, and track email campaigns that help you build a strong customer base."
They don't have 40 million users. They have 40 million targets.
Of course they don't get many complaints. If you search for "zoho opt out", you get sent to a page with a HTTP 400 error.[2]
[1] https://www.zoho.com/campaigns [2] https://help.zoho.com/portal/kb/articles/what-does-email-opt...
400 Bad Request in Firefox.
curl:
curl https://help.zoho.com
<html>
<head><title>400 Bad Request</title></head>
<body bgcolor="white">
<center><h1>400 Bad Request</h1></center>
</body>
</html>