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:

  ladakli na seznam.cz
    SMTP error from remote mail server after RCPT TO:<ladakli na seznam.cz>:
    host mx1.seznam.cz [77.75.78.42]: 550 5.1.1 Sorry, no mailbox here by that name.
  ait.jun na seznam.cz
    SMTP error from remote mail server after RCPT TO:<ait.jun na seznam.cz>:
    host mx1.seznam.cz [77.75.78.42]: 550 5.1.1 Sorry, no mailbox here by that name.
  nejeto na seznam.cz
    SMTP error from remote mail server after RCPT TO:<nejeto na seznam.cz>:
    host mx1.seznam.cz [77.75.78.42]: 550 5.1.1 Sorry, no mailbox here by that name.
  89sniper na seznam.cz
    SMTP error from remote mail server after RCPT TO:<89sniper na seznam.cz>:
    host mx1.seznam.cz [77.75.78.42]: 550 5.1.1 Sorry, no mailbox here by that name.