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Accepted Answer
The issue is that by default, WordPress uses PHP’s mail() function and nothing more. Mail sent using this function is inevitably going to end up in spam/junk due to the fact that there’s no authorization.
It’s simple to create a function that runs mail() through a loop and sends 10k-100k e-mails in a very short period of time complete with random messages and e-mails. Since there’s no authorization to an e-mail server, via SMTP or API, the mail comes through from whatever the hostname of the VPS or Droplet happens to be and gets flagged (as it should).
What I recommend using using a transactional e-mail provider, such as SparkPost. The service is free up to 100k e-mails per month, and it’s one that I recommend to most that I work with who need e-mail but don’t want to manage their own mail server.
There’s a WordPress plugin to help in connecting as well.
https://wordpress.org/plugins/sparkpost/
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Of course, there are others: Mandrill, MailGun, and SendGrid, just to name a few.
Hello, all
You can make sure that your mailing list is fully opted-in and that you’re using SMTP authentication.
Also to test the mail score of your emails you can use a website like:
and then send a valid test - an exact email with a valid - subject, message body, full signatures and attachments.
Regards, Alex