Just found out about this, normally we have different custom Mail-From for our newsletter and transactional email. But apparently we need a whole subdomain to separate the reputation: Instead of [[email protected]](mailto:[email protected]) for everything, we should go with e.g.: [[email protected]](mailto:[email protected]) for newsletters and [[email protected]](mailto:[email protected]) for transactional and keep [[email protected]](mailto:[email protected]) strictly for our employees everyday emails. An engineer advised me to even go further and change the From-Address too, even with different subdomains, example [[email protected]](mailto:[email protected]) for newsletters and [[email protected]](mailto:[email protected]) even tho they have different subdomains and different Custom Mail-From.…