My Magento 2 send an email when I register in the newsletter, but I receive that exception all time:
How can I solve it? Thanks
To send email from Magento you need to configure an email SMTP server on the web host/server. Magento uses the PHP
mail() method by default, although there are extensions you can install to override this behavior.
If it's JUST the Newsletter that's not sending, and other emails like Registration and Password Reset are sending fine, then it could be some other problem and you will need to post more information.
It could be a PHP ini configuration issue with the
sendmail, or an incorrect hostname, etc.
But as a Magento Certified Developer I assume you already know all of this? Sorry if I misunderstood your question and gave too many obvious answers.
For Magento 2.3.1 check out this bug: https://github.com/magento/magento2/issues/20033