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:

  b.rogers na volny.cz
    SMTP error from remote mail server after RCPT TO:<b.rogers na volny.cz>:
    host cbx.virusfree.cz [31.7.241.26]: 554 5.7.1 <b.rogers na volny.cz>:
    Recipient address rejected: Access denied, user does not exist
  kotek.leo na muhodonin.cz
    SMTP error from remote mail server after RCPT TO:<kotek.leo na muhodonin.cz>:
    host mail.muhodonin.cz [31.192.64.130]: 550 5.1.1 Mailbox <kotek.leo na muhodonin.cz> does not exist