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:

  cd.dfdf na seznam.cz
    SMTP error from remote mail server after RCPT TO:<cd.dfdf na seznam.cz>:
    host mx1.seznam.cz [77.75.76.42]: 550 5.1.1 Sorry, no mailbox here by that name.
  salam04 na seznam.cz
    SMTP error from remote mail server after RCPT TO:<salam04 na seznam.cz>:
    host mx1.seznam.cz [77.75.76.42]: 550 5.1.1 Sorry, no mailbox here by that name.
  nuffs na seznam.cz
    SMTP error from remote mail server after RCPT TO:<nuffs na seznam.cz>:
    host mx1.seznam.cz [77.75.76.42]: 550 5.1.1 Sorry, no mailbox here by that name.
  ostrava-jih na seznam.cz
    SMTP error from remote mail server after RCPT TO:<ostrava-jih na seznam.cz>:
    host mx1.seznam.cz [77.75.76.42]: 550 5.1.1 Sorry, no mailbox here by that name.