There is one condition in Newsletter Email's Model file here..
vendor/magento/module-newsletter/Model/Subscriber.php
if ($this->getImportMode()) {
return $this;
}
If in this function you will get true
as an Import Mode then these all functions will not work for newsletter emails.
- sendConfirmationRequestEmail()
- sendConfirmationSuccessEmail()
- sendUnsubscriptionEmail()
If you are using MailChimp for emails then you will get this issue, Because there is one setting available in MailChimp Configuration.
Store > Configuration > MAILCHIMP > Mailchimp > Mailchimp General Configuration > Magento always manage emails
In this setting you need to select "Yes", Because if you will select "No" there then Mailchimp will use Import Mode is Yes. So from Magento Customer will not get any newsletter emails.
You can run below command to enable that setting without changing that in configuration.
php bin/magento config:set mailchimp/general/magentoemail 1
php bin/magento cache:clean
php bin/magento cache:flush
Hope this will help you!