after some changes I received the information "Virtualmin's configuration has not been checked since it was last updated. Click the button below to verify it now. Re-check and refresh configuration".
When I press the button, the check claims: "Your Postfix configuration is missing the system's mail hostname domain.tld from the mydestination line, which will cause mail to bounce."
First problem: the hostname is host.domain.tld, the domain name is domain.tld - is this just a failure in the right wording?
Second problem: my main.cf is correct and works seamlessly:
### Domain, host etc
mydomain = domain.tld
myhostname = host.domain.tld
# Name used in outgoing mails, default: myhostname, better: mydomain
myorigin = $mydomain
# Domains to receive mail for
mydestination = localhost, localhost.$mydomain, $myhostname, $mydomain
Why is Virtualmin complaining about this configuration or considering it as erroneous?