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:

  m.dassler na centrum.cz
    SMTP error from remote mail server after RCPT TO:<m.dassler na centrum.cz>:
    host cbx.virusfree.cz [5.180.49.37]: 554 5.7.1 <m.dassler na centrum.cz>:
    Recipient address rejected: Access denied, user does not exist
  mike49 na tiscali.cz
    SMTP error from remote mail server after end of data:
    host tbx.virusfree.cz [5.180.49.36]: 554 message refused (#5.7.1) - for more information visit https://www.virusfree.cz/cs/help