Need help; cannot send email in gnus and emacs anymore; 550 relay not permitted

[physiculus]

hello,
unfortunately i cannot send emails from my four accounts anymore.
it's only a problem from inside emacs / gnus. so i think, there is any
misconfiguration.

how can i check, whats going wrong?

here is the debugger output.


Debugger entered--Lisp error: (error "Sending failed: 550 relay not
permitted") signal(error ("Sending failed: 550 relay not permitted"))
  error("Sending failed: %s" "550 relay not permitted")
  smtpmail-send-it()
  message-smtpmail-send-it()
  message-multi-smtp-send-mail()
  message--send-mail-maybe-partially()
  message-send-mail(nil)
  message-send-via-mail(nil)
  message-send(nil)
  message-send-and-exit(nil)
  funcall-interactively(message-send-and-exit nil)
  call-interactively(message-send-and-exit nil nil)
  command-execute(message-send-and-exit)


regards
poul