... this may be because the newsletter signup was accessed via the domain "domain.tld", while the TYPO3 system is installed on the subdomain "www.domain.tld".
This means that an attempt is being made to violate the "same-origin policy" of Ajax, resulting in incorrect execution of the newsletter extension. The simplest solution is to redirect all requests from "domain.tld" to the subdomain "www.domain.tld".
