Kmail: "sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)")
What can I do? Someone who knows how to setup
kmail correctly? Nor automatic or hand procedure works.
This is not an error of KMail, but from the remote SMTP server it is talking to.
The server (MTA) is complaining about your request. Probably you are trying to send mail and using an SMTP server which does not allow relaying in your current configuration.
Some general solutions to this: