I have just setup a Virtualmin server, but mail clients can't send e-mail because of this error.
I have tried setting "My server requires authentication" for outgoing mail, but that just asks for the password again.
Checking mail works fine. In usermin it works fin to send e-mail to everyone.
What do I do, how do I configure virtualmin?
It's working now, have no idea how I got it to work ....