Mail delivery failed: returning message to sender

[Mail Delivery System]

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  slunicko2004 na volny.cz
    SMTP error from remote mail server after RCPT TO:<slunicko2004 na volny.cz>:
    host cbx.virusfree.cz [5.180.49.37]: 554 5.7.1 <slunicko2004 na volny.cz>:
    Recipient address rejected: Access denied, user does not exist
  wejrf na wejj.cz
    Unrouteable address